Resist composition and patterning process

ABSTRACT

To a resist composition comprising a polymer which changes its alkali solubility under the action of an acid as a base resin, is added a copolymer comprising recurring units containing a carboxylic acid ammonium salt and recurring units containing at least one fluorine atom as an additive. The composition is suited for immersion lithography.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-086625 filed in Japan on Mar. 29, 2007, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to resist compositions for use in the lithography technology for the microfabrication of semiconductor devices or the like, especially the immersion photolithography utilizing an ArF excimer laser of wavelength 193 nm as the light source and interposing water between a projection lens and a wafer. It also relates to a patterning process using the resist compositions.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSI devices, the pattern rule is made drastically finer. The photolithography which is currently on widespread use in the art is approaching the essential limit of resolution determined by the wavelength of a light source.

As the light source used in the lithography for resist pattern formation, g-line (436 nm) or i-line (365 nm) from a mercury lamp was widely used. One means believed effective for further reducing the feature size is to reduce the wavelength of exposure light. For the mass production process of 64 MB dynamic random access memories (DRAM, processing feature size 0.25 μm or less) and later ones, the exposure light source of i-line (365 nm) was replaced by a KrF excimer laser having a shorter wavelength of 248 nm.

However, for the fabrication of DRAM with a degree of integration of 256 MB and 1 GB or more requiring a finer patterning technology (processing feature size 0.2 μm or less), a shorter wavelength light source is required. Over a decade, photolithography using ArF excimer laser light (193 nm) has been under active investigation.

It was expected at the initial that the ArF lithography would be applied to the fabrication of 180-nm node devices. However, the KrF excimer lithography survived to the mass-scale fabrication of 130-nm node devices. So, the full application of ArF lithography started from the 90-nm node. The ArF lithography combined with a lens having an increased numerical aperture (NA) of 0.9 is considered to comply with 65-nm node devices.

For the next 45-nm node devices which required an advancement to reduce the wavelength of exposure light, the F₂ lithography of 157 nm wavelength became a candidate. However, for the reasons that the projection lens uses a large amount of expensive CaF₂ single crystal, the scanner thus becomes expensive, hard pellicles are introduced due to the extremely low durability of soft pellicles, the optical system must be accordingly altered, and the etch resistance of resist is low; the postponement of F₂ lithography and the early introduction of ArF immersion lithography were advocated (see Proc. SPIE Vol. 4690 xxix).

In the ArF immersion lithography, the space between the projection lens and the wafer is filled with water. Since water has a refractive index of 1.44 at 193 nm, pattern formation is possible even using a lens with NA of 1.0 or greater. Theoretically, it is possible to increase the NA to 1.35. The resolution is improved by an increment of NA. A combination of a lens having NA of at least 1.2 with ultra-high resolution technology suggests a way to the 45-nm node (see Proc. SPIE Vol. 5040, p 724).

However, for resist materials, as the circuit line width is reduced, the influence of acid diffusion on contrast becomes more serious. This is because the pattern size is approaching the diffusion length of acid, and leads to a lowering of mask fidelity and a degradation of pattern rectangularity. Therefore, in order to take full advantage of the reduced wavelength of a light source and the increased NA, it is necessary to increase the dissolution contrast over prior art materials and to restrain the acid diffusion.

With respect to the immersion lithography, several problems associated with the presence of water on resist were pointed out. Because the photoacid generator in the resist film, the acid generated therefrom upon exposure, and the amine compound added to the resist as a quencher can be leached in water in contact with the resist film, pattern profile changes occur. The pattern collapses due to swelling of the resist film with water.

With respect to the leaching of resist components into water, a study started from the standpoint of preventing the projection lens of the lithography system from contamination. Several lithography system manufacturers proposed the limit of leach-outs.

For overcoming these problems, it was proposed to provide a protective coating of perfluoroalkyl compound between the resist film and water (see the 2nd Immersion Workshop, Jul. 11, 2003, Resist and Cover Material Investigation, for Immersion Lithography). The provision of such a protective coating avoids direct contact between the resist film and water and inhibits the resist film from being leached with water.

However, protective coatings made of perfluoroalkyl compounds use fluorocarbons like Freon® as the diluent for controlling a coating thickness. As is well known, the use of fluorocarbons is a consideration in view of environmental protection. In addition, the protective coating must be stripped using fluorocarbon, prior to development of the resist film. Therefore, special units for coating and stripping of the protective film must be added to the existing system. Fluorocarbon solvents add to the expense. These factors raise serious problems on practical use.

One means proposed for mitigating practical drawbacks of the protective film of solvent stripping type is a protective film of the type which is soluble in alkaline developer (JP-A 2005-264131). The alkali-soluble protective film is epoch-making in that it eliminates a need for a stripping step or a special stripping unit because it can be stripped off at the same time as the development of a photoresist film.

The ArF immersion lithography systems commercially available at the present are designed such that water is partly held between the projection lens and the wafer rather than immersing the resist-coated substrate fully in water, and exposure is carried out by scanning the wafer-holding stage at a speed of 300 to 550 mm/sec. Because of such high-speed scanning, water cannot be held between the projection lens and the wafer, and water droplets are left on the surface of the resist film or protective film after scanning. It is believed that residual droplets cause defective pattern formation.

To eliminate the droplets remaining on the surface of the photoresist or protective film after scanning, it is necessary to improve the flow or mobility of water on the relevant coating film. It is reported that the number of defects associated with the immersion lithography can be reduced by increasing the receding contact angle of the photoresist or protective film with water. See 2nd International Symposium on Immersion Lithography, 12-15 September, 2005, Defectivity data taken with a full-field immersion exposure tool, Nakano et al. It is noted that the method of measuring a receding contact angle includes a sliding method of inclining a substrate and a suction method of sucking up water, with the sliding method being widely accepted.

If residues are left on the resist film after development, there arise defects which are known as blobs. The blob defects occur because the protective coating or resist material is precipitated during rinsing after development and deposited on the resist film again, and are found more often when the resist film after development is more hydrophobic. For the resist for use in the immersion lithography in combination with a protective coating, if mixing occurs between the protective coating and the resist coating, the hydrophobic protective coating can be left on the surface of the resist coating after development, leading to blob defects on the resist coating. It is then necessary to prevent intermixing between the protective coating and the resist coating so that no protective coating is left after development.

In the electron beam writing lithography, there arises a problem that electric charges accumulate in the resist coating during exposure. The charge accumulation may be avoided by forming a water-soluble antistatic coating on the photoresist. The antistatic coating is formed of materials comprising a water-soluble polymer and an ammonium salt of sulfonic acid added thereto. The negative charges generated by electron beam exposure are transferred through the antistatic coating to the earth side of a wafer chuck where they are released. However, the antistatic coating, when formed on the photoresist coating, adds an additional coating step and a coating material cost to the overall process, which are undesirable. It would be desirable to have a photoresist having an antistatic function, eliminating a need for a separate antistatic coating.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a photoresist composition which when coated as photoresists, forms a resist layer having a surface modified so as to improve dissolution contrast for thereby improving pattern rectangularity and mask fidelity, wherein in the immersion lithography, the resist layer prevents intermixing between resist and protective layers when a protective layer is formed on the resist layer, and the resist layer on its surface is more hydrophilic after exposure and development, thus preventing blob defects from generating, and which composition, when used as electron beam resists, is effective for preventing accumulation of charge on the resist film surface due to charging during e-beam exposure.

Another object is to provide a patterning process using the resist composition.

In a first aspect, the invention provides a resist composition comprising a polymer which changes its alkali solubility under the action of an acid as a base resin, and a copolymer comprising recurring units containing a carboxylic acid ammonium salt and recurring units containing at least one fluorine atom as an additive.

In a preferred embodiment, the copolymer has the general formula (1).

Herein R⁰, R³, R⁵, and R⁸ are each independently hydrogen or methyl. X₁ and Y₂ are each independently a single bond, —O—R¹⁰—, —C(═O)—O—R¹⁰—, —C(═O)—NH—R¹⁰—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹⁰ is a straight, branched or cyclic C₁-C₁₀ alkylene group which may contain an ester (—COO—) or ether (—O—) group. The subscript n is 1 or 2. In case of n=1, Y₁ is a single bond, —O—R¹⁰—, —C(═O)—O—R¹⁰—, —C(═O)—NH—R¹⁰—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹⁰ is as defined above. In case of n=2, Y₁ is —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight or branched C₁-C₄ alkylene group with one hydrogen atom eliminated, or a phenylene group with one hydrogen atom eliminated, wherein R¹⁰¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group with one hydrogen atom eliminated which may contain an ester or ether group. X₂ is a single bond, —O—R¹¹—, —C(═O)—O—R¹¹—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group which may contain an ester or ether group and which may contain a fluorine atom. R¹ and R⁴ are each independently hydrogen, a straight, branched or cyclic C₁-C₂₀ alkyl or C₁-C₂₀ alkenyl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom, or a C₆-C₁, aryl group, two or three R¹ or two, three or four R⁴ may bond together to form a ring of 3 to 20 carbon atoms. R² is a straight, branched or cyclic C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl or C₆-C₁₄ aryl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom. R⁶ is a straight, branched or cyclic C₁-C₁₂ alkylene group. R⁷ is hydrogen, fluorine, methyl, trifluoromethyl or difluoromethyl, or R⁷ may bond with R⁶ to form a ring which may contain an ether group, fluorinated alkylene group or trifluoromethyl group. R⁹ is a straight, branched or cyclic C₁-C₂₀ alkyl group which has at least one fluorine atom substituted thereon and which may contain an ether, ester or sulfonamide group. The subscripts (a-1), (a-2), (b-1), and (b-2) are numbers in the range: 0≦(a-1)<1.0, 0≦(a-2)<1.0, 0≦(a-1)+(a-2)<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦(a-1)+(a-2)+(b-1)+(b-2)≦1.0.

Typically the resist composition is a chemically amplified resist composition which may be either positive or negative. When the resist composition is positive, the base resin is specifically a polymer comprising recurring units having acid labile groups and recurring units having hydroxy groups and/or adhesive groups of lactone ring.

Where the base resin includes recurring units having hydroxy groups and/or adhesive groups of lactone ring, the chemically amplified positive resist composition ensures tight adhesion to a substrate. Where the base resin includes recurring units having acid labile groups, the acid labile groups are deprotected with the acid generated by the acid generator during exposure so that the exposed area of resist is converted to be soluble in a developer, ensuring that a pattern is formed at a very high precision.

Also preferably the resist composition further comprises at least one member selected from among an organic solvent, a basic compound, a dissolution regulator, a crosslinker, and a surfactant.

The inclusion of an organic solvent can facilitate to coat the resist composition to substrates or the like. The inclusion of a basic compound can hold down the diffusion rate of acid within the resist film, leading to a further improved resolution. The inclusion of a dissolution regulator can increase the difference in dissolution rate between exposed and unexposed areas, leading to a further improved resolution. The addition of a surfactant can further facilitate or control the coating operation of the resist composition. For the chemically amplified resist composition which is negative, a crosslinker is compounded.

In another aspect, the invention provides a pattern forming process comprising the steps of applying the aforementioned resist composition onto a substrate to form a coating, heat treating the coating and exposing it to high-energy radiation, and developing the exposed coating with a developer. The step of heat treatment may be included after the exposing step and before the developing step. The process may further include subsequent steps such as etching, resist removal and cleaning. Preferably the high-energy radiation has a wavelength of 180 to 250 nm.

In preferred embodiments, the exposing step is by immersion lithography involving exposing the coating to high-energy radiation through a liquid. The process may further comprise the step of forming a protective coating so that the protective coating intervenes between the photoresist coating and the liquid during the immersion lithography. The protective coating is typically an alkali-soluble protective film based on a polymer having α-trifluoromethylhydroxy groups.

The immersion lithography may involve using high-energy radiation having a wavelength of 180 to 250 nm, introducing a liquid between the resist-coated substrate and a projection lens, and exposing the substrate to the high-energy radiation through the liquid. The liquid is typically water.

BENEFITS OF THE INVENTION

The inventive resist composition has the advantages of pattern rectangularity and mask fidelity. The photoresist film formed from the composition has a surface which is hydrophilic enough to prevent blob defects from generating on the resist film after development. The resist film also prevents intermixing between the resist film and a protective layer which is formed in the immersion lithography for protecting the resist film, thus preventing the pattern profile from being degraded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item.

As used herein, the notation (C_(n)-C_(m)) means a group containing from n to m carbon atoms per group.

The abbreviation “phr” refers to parts by weight per 100 parts by weight of resin.

The inventors have found that (1) a photoresist composition comprising a specific polymer additive compounded therein exhibits a very high resolution and is improved especially in pattern rectangularity and mask fidelity. In the immersion lithography, a protective layer is formed on a photoresist layer, and water is held between the protective layer and a projection lens. We have also found that (2) a photoresist layer formed from the composition is effective for preventing intermixing between the resist layer and the protective layer; and (3) the photoresist layer presents a surface which is hydrophilic after development, for preventing defect generation. Further studying the composition and compounding of the polymer additive, we have completed the invention.

Polymeric Surfactant

The resist composition of the invention is defined as comprising a polymer which changes its alkali solubility under the action of an acid as a base resin, and a copolymer comprising recurring units containing a carboxylic acid ammonium salt and recurring units containing at least one fluorine atom as an additive.

In a preferred embodiment, the recurring units containing a carboxylic acid ammonium salt and recurring units containing at least one fluorine atom are represented by the general formula (1).

Herein R⁰, R³, R⁵, and R⁸ are each independently hydrogen or methyl. X₁ and Y₂ are each independently a single bond, —O—R¹⁰—, —C(═O)—O—R¹⁰—, —C(═O)—NH—R¹⁰—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹⁰ is a straight, branched or cyclic C₁-C₄ alkylene group which may contain an ester (—COO—) or ether (—O—) group. The subscript n is 1 or 2. In case of n=1, Y₁ is a single bond, —O—R¹¹—, —C(═O)—O—R¹¹—, —C(═O)—NH—R¹¹—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹⁰ is as defined above. In case of n=2, Y₁ is —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight or branched C₁-C₄ alkylene group with one hydrogen atom eliminated, or a phenylene group with one hydrogen atom eliminated, wherein R¹¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group with one hydrogen atom eliminated which may contain an ester or ether group. X₂ is a single bond, —O—R¹¹═, —C(═O)—O—R¹¹—, a straight or branched C₁-C₄ alkylene, or phenylene group, wherein R¹¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group which may contain an ester or ether group and which may contain a fluorine atom. R¹ and R⁴ are each independently hydrogen, a straight, branched or cyclic C₁-C₂₀ alkyl or C₂-C₂₀ alkenyl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom, or a C₆-C₁₀ aryl group, two or three R¹ or two, three or four R⁴ may bond together to form a ring of 3 to 20 carbon atoms. R² is a straight, branched or cyclic C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl or C₆-C₁₄ aryl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom. R⁶ is a straight, branched or cyclic C₁-C₁₂ alkylene group. R⁷ is hydrogen, fluorine, methyl, trifluoromethyl or difluoromethyl, or R⁷ may bond with R⁶ to form an aliphatic ring of 3 to 12 carbon atoms, preferably 3 to 10 carbon atoms, with the carbon atom to which they are attached, which ring may contain an ether group, fluorinated alkylene group or trifluoromethyl group. R⁹ is a straight, branched or cyclic C₁-C₂₀ alkyl group which has at least one fluorine atom substituted thereon and which may contain an ether, ester or sulfonamide group. The subscripts (a-1), (a-2), (b-1), and (b-2) are numbers in the range: 0≦(a-1)<1.0, 0≦(a-2)<1.0, 0<(a-1)+(a-2)<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦(a-1)+(a-2)+(b-1)+(b-2)≦1.0.

The photoresist composition of the invention is characterized by the addition of a surfactant in polymeric form having a carboxylic acid ammonium salt and a fluoroalkyl group, as represented by formula (1). In resist compositions based on alicyclic polymers for use in the ArF lithography, a sulfonic acid fluorinated at α-position such as perfluorobutanesulfonic acid is used as the acid generator. Due to the electron withdrawing effect at α-position, this sulfonic acid has a very high acidity enough for efficient deprotection reaction to proceed. Upon exposure, the acid generator generates a sulfonic acid fluorinated at α-position, which undergoes anion exchange with the carboxylic acid ammonium salt in the polymeric surfactant of formula (1), yielding a sulfonic acid ammonium salt and a carboxylic acid. The anion exchange occurs because the α-fluorinated sulfonic acid has a higher acid strength than the carboxylic acid. The carboxylic acid thus yielded is a weak acid which has not an acid strength sufficient for deprotection reaction to proceed. The carboxylic acid ammonium salt functions as a quencher to the acid generated upon exposure. While the concentration distribution of acid generated is such that a layer closer to the surface has a higher acid concentration, and shows more noticeable changes under lower optical contrast conditions, the addition of the polymeric surfactant of formula (1) prevents the concentration of acid generated in the surface layer from becoming excessive and thus improves dissolution contrast, thereby forming a pattern in a rectangular profile and improving mask fidelity. In the case of a hole pattern, side lobe resistance is improved. When a photoresist layer is formed, the carboxylic acid ammonium salt is oriented on the resist layer surface, whereby the resist layer surface becomes hydrophilic, restraining occurrence of blob defects following development. In one exemplary immersion lithography, following formation of a photoresist layer, a protective coating is applied thereon as a topcoat. The protective coating is preferably formed of such a material that meets both alkali solubility and water repellency, specifically a material comprising a polymer having α-trifluoromethylhydroxy groups as a base in a solvent in which the resist layer is not dissolved and which is selected from higher alcohols of 4 or more carbon atoms, ethers, alkanes, fluorine atoms and the like. Since the surfactant in polymeric form having a carboxylic acid ammonium salt and a fluoroalkyl group according to the invention is not soluble at all in the solvent for the protective coating material, it provides a barrier layer for preventing intermixing between the protective layer and the resist layer. Thus, the profile of a resist pattern after development remains unchanged whether or not a protective layer is used. A resist pattern of good profile is always obtainable.

Examples of suitable polymerizable monomers from which recurring units (a-1) in formula (1) are derived are given below.

Herein R⁰ and R² are as defined above.

Examples of the carboxylic acid anion R²COO⁻ include formate, acetate, propionate, butyrate, isobutyrate, valerate, isovalerate, pivalate, hexanoate, octanoate, cyclohexanecarboxylate, cyclohexylacetate, laurate, myristate, palmitate, stearate, phenylacetate, diphenylacetate, phenoxyacetate, mandelate, benzoylformate, cinnamate, dihydrocinnamate, benzoate, methylbenzoate, salicylate, naphthalenecarboxylate, anthracenecarboxylate, anthraquinonecarboxylate, hydroxyacetate, pivalate, lactate, methoxyacetate, 2-(2-methoxyethoxy)acetate, 2-(2-(2-methoxyethoxy)ethoxy)acetate, diphenolate, monochloroacetate, dichloroacetate, trichloroacetate, trifluoroacetate, pentafluoropropionate, and heptafluorobutyrate anions. Also included are mono-anions of dicarboxylic acids such as succinic acid, tartaric acid, glutaric acid, pimelic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, cyclohexanedicarboxylic acid, and cyclohexenedicarboxylic acid.

Where the cation of the carboxylic acid ammonium salt in recurring units (a-1) is a primary, secondary or tertiary ammonium salt, the carboxylic acid salt can also be obtained by polymerizing an amino compound having a double bond and then effecting neutralization reaction with a carboxylic acid.

Examples of suitable polymerizable monomers from which recurring units (a-2) in formula (1) are derived are given below.

Herein R³ and R⁴ are as defined above.

Examples of the ammonium cation serving as a pairing ion with carboxylic acid in recurring units (a-2) include ammonium cations resulting from protonation of the nitrogen atom of the following compounds; ammonia, primary, secondary and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having carboxyl group, nitrogen-containing compounds having sulfonyl group, nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, and alcoholic nitrogen-containing compounds, as well as quaternary ammonium cations.

Illustrative examples of primary aliphatic ammonium include methylammonium, ethylammonium, n-propylammonium, isopropylammonium, n-butylammonium, isobutylammonium, sec-butylammonium, tert-butylammonium, pentylammonium, tert-amylammonium, cyclopentylammonium, hexylammonium, cyclohexylammonium, heptylammonium, octylammonium, nonylammonium, decylammonium, dodecylammonium, cetylammonium, aminomethylammonium, and 2-aminoethylammonium. Examples of secondary aliphatic ammonium include dimethylammonium, diethylammonium, di-n-propylammonium, diisopropylammonium, di-n-butylammonium, diisobutylammonium, di-sec-butylammonium, dipentylammonium, dicyclopentylammonium, dihexylammonium, dicyclohexylammonium, diheptylammonium, dioctylammonium, dinonylammonium, didecylammonium, didodecylammonium, dicetylammonium, methyl(methylamino)methylammonium, and methyl-2-(methylamino)ethylammonium. Examples of tertiary aliphatic ammonium include trimethylammonium, triethylammonium, tri-n-propylammonium, triisopropylammonium, tri-n-butylammonium, triisobutylammonium, tri-sec-butylammonium, tripentylammonium, tricyclopentylammonium, trihexylammonium, tricyclohexylammonium, triheptylammonium, trioctylammonium, trinonylammonium, tridecylammonium, tridodecylammonium, tricetylammonium, dimethyl(dimethylamino)methylammonium, and dimethyl(2-dimethylaminoethyl)ammonium.

Exemplary of mixed ammoniums are dimethyl ethyl ammonium, methyl ethyl propyl ammonium, benzyl ammonium, phenethyl ammonium, and benzyl dimethyl ammonium. Examples of aromatic ammoniums and heterocyclic ammoniums include anilinium derivatives (e.g., anilinium, N-methylanilinium, N-ethylanilinium, N-propylanilinium, N,N-dimethylanilinium, 2-methylanilinium, 3-methylanilinium, 4-methylanilinium, ethylanilinium with an arbitrary substitution position, propylanilinium with an arbitrary substitution position, trimethylanilinium with an arbitrary substitution position, 2-nitroanilinium, 3-nitroanilinium, 4-nitroanilinium, 2,4-dinitroanilinium, 2,6-dinitroanilinium, 3,5-dinitroanilinium, and N,N-dimethyltoluidinium with an arbitrary substitution position), diphenyl(p-tolyl)ammonium, methyldiphenylammonium, triphenylammonium, aminophenylammonium with an arbitrary substitution position, naphthylammonium, aminonaphthylammonium with an arbitrary substitution position, pyrrolinium derivatives (e.g., pyrrolinium, 2H-pyrrolinium, 1-methylpyrrolinium, 2,4-dimethylpyrrolinium, 2,5-dimethylpyrrolinium, and N-methylpyrrolinium), oxazolium derivatives (e.g., oxazolium and isooxazolium), thiazolium derivatives (e.g., thiazolium and isothiazolium), imidazolium derivatives (e.g., imidazolium, 4-methylimidazolium, and 4-methyl-2-phenylimidazolium), pyrazolium derivatives, furazanium derivatives, pyrrolinium derivatives (e.g., pyrrolinium, 2-methyl-1-pyrrolinium), pyrrolidinium derivatives (e.g., pyrrolidinium, N-methylpyrrolidinium, pyrrolidinonium, and N-methylpyrolidonium), imidazolinium derivatives, imidazolidinium derivatives, pyridinium derivatives (e.g., pyridinium, methylpyridinium, ethylpyridinium, propylpyridinium, butylpyridinium, 4-(1-butylpentyl)pyridinium, dimethylpyridinium, trimethylpyridinium, triethylpyridinium, phenylpyridinium, 3-methyl-2-phenylpyridinium, 4-tert-butylpyridinium, diphenylpyridinium, benzylpyridinium, methoxypyridinium, butoxypyridinium, dimethoxypyridinium, 4-pyrrolidinopyridinium, 2-(1-ethylpropyl)pyridinium, aminopyridinium, and dimethylaminopyridinium), pyridazinium derivatives, pyrimidinium derivatives, pyrazinium derivatives, pyrazolinium derivatives, pyrazolidinium derivatives, piperidinium derivatives, piperazinium derivatives, molpholinium derivatives, indolinium derivatives, isoindolinium derivatives, 1H-indazolinium derivatives, indolinium derivatives, qunolinium derivatives (e.g., quinolinium), isoquinolinium derivatives, cinnolinium derivatives, quinazolinium derivatives, quinoxalinium derivatives, phthalazinium derivatives, purinium derivatives, pteridinium derivatives, carbazolium derivatives, phenanthridinium derivatives, acridinium derivatives, phenazinium derivatives, 1,10-phenanthrolinium derivatives, and protonated forms of heterocyclic compounds having a partial structure of amidine skeleton, such as DBU (1,8-diazabicyclo[5.4.0]-7-undecene) and DBN (1,5-diazabicyclo[4.3.0]-5-nonene).

Examples of suitable nitrogen-containing compounds having carboxyl group include carboxyphenylammonium, carboxyindolinium, and protonated forms of amino acid derivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, and methoxyalanine). One exemplary nitrogen-containing compound having sulfonyl group is 3-pyridiniumsulfonic acid. Examples of suitable nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, and alcoholic nitrogen-containing compounds include 2-hydroxypyridinium, hydroxyanilinium with an arbitrary substitution position, hydroxy-methyl-anilinium with an arbitrary substitution position, hydroxyquinolinium, dihydroxyquinolinium, 2-hydroxyethylammonium, bis(2-hydroxyethyl)ammonium, tris(2-hydroxyethyl)ammonium, ethylbis(2-hydroxyethyl)ammonium, diethyl(2-hydroxyethyl)ammonium, hydroxypropylammonium, bis(hydroxypropyl)ammonium, tris hydroxypropyl)ammonium, 4-(2-hydroxyethyl)morpholinium, 2-(2-hydroxyethyl)pyridinium, 1-(2-hydroxyethyl)piperazinium, 1-[2-(2-hydroxyethoxy)ethyl]piperazinium, (2-hydroxyethyl)piperazinium, 1-(2-hydroxyethyl)pyrrolidinium, 1-(2-hydroxyethyl)-2-pyrrolidinonium, 2,3-dihydroxypropylpiperidinium, 2,3-dihydroxypropylpiperolidinium, 8-hydroxyjulolidinium, and 3-hydroxyquinuclidinium.

Further exemplary are ammonium cations of the following general formula (2)-1. HN⁺(X)_(n)(Y)_(3-n)  (2)-1 In the formula, n is equal to 1, 2 or 3; side chain X which may be the same or different is selected from groups of the following general formulas (X1), (X2) and (X3), and two or three X's may bond together to form a ring; and side chain Y which may be the same or different is hydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbon atoms which may contain an ether or hydroxyl group.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight or branched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independently hydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which may contain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³ is a single bond or a straight or branched C₁-C₄ alkylene group; and R³⁰⁶ is a straight, branched or cyclic C₁-C₂₀ alkyl group which may contain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (2)-1 include tris(2-methoxymethoxyethyl)ammonium, tris{2-(2-methoxyethoxy)ethyl}ammonium, tris{2-(2-methoxyethoxymethoxy)ethyl}ammonium, tris{2-(1-methoxyethoxy)ethyl}ammonium, tris{2-(1-ethoxyethoxy)ethyl}ammonium, tris{2-(1-ethoxypropoxy)ethyl}ammonium, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]ammonium, protonated 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane, protonated 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, protonated 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, protonated 1-aza-12-crown-4, protonated 1-aza-15-crown-5, protonated 1-aza-18-crown-6, tris(2-formyloxyethyl)ammonium, tris(2-acetoxyethyl)ammonium, tris(2-propionyloxyethyl)ammonium, tris(2-butyryloxyethyl)ammonium, tris(2-isobutyryloxyethyl)ammonium, tris(2-valeryloxyethyl)ammonium, tris(2-pivaloyloxyethyl)ammonium, N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylammonium, tris(2-methoxycarbonyloxyethyl)ammonium, tris(2-tert-butoxycarbonyloxyethyl)ammonium, tris[2-(2-oxopropoxy)ethyl]ammonium, tris[2-(methoxycarbonylmethyl)oxyethyl]ammonium, tris[2-(tert-butoxycarbonylmethyloxy)ethyl]ammonium, tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]ammonium, tris(2-methoxycarbonylethyl)ammonium, tris(2-ethoxycarbonylethyl)ammonium, N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylammonium, N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylammonium, N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylammonium, N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylammonium, N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylammonium, N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylammonium, N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylammonium, N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylammonium, N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylammonium, N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylammonium, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylammonium, N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylammonium, N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylammonium, N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylammonium, N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylammonium, N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylammonium, N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylammonium, N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylammonium, N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylammonium, N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylammonium, N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]ammonium, N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]ammonium, N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]ammonium, N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]ammonium, N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]ammonium, N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]ammonium, N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]ammonium, N-butyl-bis[2-(methoxycarbonyl)ethyl]ammonium, N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]ammonium, N-methyl-bis(2-acetoxyethyl)ammonium, N-ethyl-bis(2-acetoxyethyl)ammonium, N-methyl-bis(2-pivaloyloxyethyl)ammonium, N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]ammonium, N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]ammonium, tris(methoxycarbonylmethyl)ammonium, tris(ethoxycarbonylmethyl)ammonium, N-butylbis(methoxycarbonylmethyl)ammonium, N-hexylbis(methoxycarbonylmethyl)ammonium, and protonated β-(diethylamino)-δ-valerolactone.

Also useful are ammonium cations having a cyclic structure represented by the following general formula (2)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀ alkylene group which may contain at least one carbonyl, ether, ester or sulfide group.

Illustrative examples of the ammonium cations having formula (2)-2 include protonated forms of 1-[2-(methoxymethoxy)ethyl]pyrrolidine, 1-[2-(methoxymethoxy)ethyl]piperidine, 4-[2-(methoxymethoxy)ethyl]morpholine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine, 4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate, 2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethyl methoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine, 1-[2-(t-butoxycarbonyloxy)ethyl]piperidine, 4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl 3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl 3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl 2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate, methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl 3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate, 2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate, tetrahydrofurfuryl 3-morpholinopropionate, glycidyl 3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate, 2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl 3-morpholinopropionate, cyclohexyl 3-piperidinopropionate, α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methyl piperidinoacetate, methyl morpholinoacetate, methyl thiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethyl morpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl 2-(2-methoxyethoxy)acetate, 2-morpholinoethyl 2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate, 2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate, 2-morpholinoethyl laurate, 2-morpholinoethyl myristate, 2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also useful are ammonium cations having a cyano group represented by the following general formulae (2)-3 to (2)-6.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are each independently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the cyano-containing ammonium cations represented by formulae (2)-3 to (2)-6 include protonated forms of 3-(diethylamino)propiononitrile, N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile, N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile, N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile, N,N-bis(2-methoxyethyl)-3-aminopropiononitrile, N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate, N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile, N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile, N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile, N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile, N,N-bis(2-hydroxyethyl)aminoacetonitrile, N,N-bis(2-acetoxyethyl)aminoacetonitrile, N,N-bis(2-formyloxyethyl)aminoacetonitrile, N,N-bis(2-methoxyethyl)aminoacetonitrile, N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate, N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile, N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile, N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile, N-cyanomethyl-N-[2-(methoxymethoxy)ethyl]aminoacetonitrile, N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile, N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile, N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinium propiononitrile, 1-piperidiniumpropiononitrile, 4-morpholiniumpropiononitrile, 1-pyrrolidiniumacetonitrile, 1-piperidiniumacetonitrile, 4-morpholiniumacetonitrile, cyanomethyl 3-diethylaminopropionate, cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl 3-diethylaminopropionate, 2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl 1-pyrrolidiniumpropionate, cyanomethyl 1-piperidiniumpropionate, cyanomethyl 4-morpholiniumpropionate, 2-cyanoethyl 1-pyrrolidiniumpropionate, 2-cyanoethyl 1-piperidiniumpropionate, and 2-cyanoethyl 4-morpholiniumpropionate.

Also included are organic nitrogen-containing compounds having an imidazolium structure and a polar functional group, represented by the general formula (2)-7.

Herein, R³¹⁰ is a straight, branched or cyclic C₂-C₂₀ alkyl group bearing at least one polar functional group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group, aryl group or aralkyl group having 1 to 10 carbon atoms.

Also included are organic nitrogen-containing compounds having a benzimidazolium structure and a polar functional group, represented by the general formula (2)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic alkyl group, aryl group or aralkyl group having 1 to 10 carbon atoms. R³¹ is a polar functional group-bearing, straight, branched or cyclic C₁-C₂₀ alkyl group, and the alkyl group contains as the polar functional group at least one group selected from among ester, acetal and cyano groups, and may additionally contain at least one group selected from among hydroxyl, carbonyl, ether, sulfide and carbonate groups.

Further included are ammonium cations having a polar functional group, represented by the general formulae (2)-9 and (2)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or ≡C—R³²³, R³¹⁶ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar functional group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms, or a pair of R³¹⁷ and R³¹⁸ and a pair of R³¹⁹ and R³²⁰, taken together, may form a benzene, naphthalene or pyridinium ring; R³²¹ is a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms; R³²² and R³²³ each are a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms, or a pair of R³²¹ and R³²³, taken together, may form a benzene or naphthalene ring.

Also included are ammonium cations having an aromatic carboxylic ester structure represented by the general formulae (2)-11 to (2)-14.

Herein R³²⁴ is a C₆-C₂₀, aryl group or C₄-C₂₀, hetero-aromatic group, in which some or all of hydrogen atoms may be replaced by halogen atoms, straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups, C₇-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀, acyloxy groups or C₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ is a C₁-C₁₀ alkyl group, in which some methylene groups may be replaced by oxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which some methylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond, methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is 0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is a nitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogen atom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen, methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair of R³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀ hetero-aromatic ring.

Further included are ammonium cations having a 7-oxanorbornane-2-carboxylic ester structure represented by the general formula (2)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkyl group. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀ aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polar functional groups selected from among ether, carbonyl, ester, alcohol, sulfide, nitrile, amine, imine, and amide and in which some hydrogen atoms may be replaced by halogen atoms. R³³⁴ and R³³⁵, taken together, may form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atoms.

Illustrative examples of the quaternary ammonium salts include tetramethylammonium, triethylmethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetraoctylammonium, didecyldimethylammonium, tridecylmethylammonium, hexadecyltrimethylammonium, stearyltrimethylammonium, phenyltrimethylammonium, benzyltrimethylammonium, benzyltriethylammonium, benzyltributylammonium, and benzyldimethylstearylammonium.

The monomer from which recurring units (a-2) are derived may be obtained by polymerizing a carboxyl group-containing compound having a double bond and neutralizing the resulting polymer with an amine into a carboxylic acid salt, or by polymerizing an alkali metal salt of a carboxylic acid having a double bond, eliminating the alkali metal from the resulting polymer, and neutralizing the polymer with an amine compound.

Examples of suitable monomers from which recurring units (b-1) having an α-trifluoromethylalcohol group in formula (1) are derived are given below.

Herein R⁵ is as defined above.

Examples of the monomers from which recurring units (b-2) in formula (1) are derived are given below.

Herein R⁸ is as defined above.

While the polymer to be added to the resist composition of the invention comprises recurring units (a-1), (a-2), (b-1), and (b-2) in formula (1), recurring units “c” having an adhesive group of lactone and/or recurring units “d” having an acid labile group may be copolymerized in the additive polymer, if desired, for the purpose of improving the miscibility thereof with the base polymer in the resist composition and/or inhibiting film slimming on the resist surface. The recurring units “c” having an adhesive group of lactone and the recurring units “d” having an acid labile group may be selected from those units used in the base polymer, which will be described later.

Desirably the polymer comprising recurring units (a-1), (a-2), (b-1), and (b-2) in formula (1) has a weight average molecular weight (Mw) of about 1,000 to about 100,000, and especially about 2,000 to about 30,000, as determined by gel permeation chromatography (GPC) using polystyrene standards. The Mw of the polymer is not limited thereto. A polymer with Mw of at least 1,000 exerts sufficient barrier property against water during immersion lithography and is effective for preventing photoresist components from being leached with water. A polymer with Mw of up to 100,000 has a sufficiently high rate of dissolution in an alkaline developer, minimizing the risk that when a resist film having the polymer incorporated therein is patterned, resin residues are left attached to the substrate.

When used in the resist composition, the polymers comprising recurring units (a-1), (a-2), (b-1), and (b-2) in formula (1) may be compounded alone or as a mixture in any desired proportion of two or more polymers having different copolymerization ratio or molecular weight or obtained through copolymerization of distinct monomers.

The subscripts (a-1), (a-2), (b-1), and (b-2) representative of copolymerization ratios (on a molar basis) of the corresponding units are in the range: 0≦(a-1)<1.0, 0≦(a-2)<1.0, 0<(a-1)+(a-2)<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦(a-1)+(a-2)+(b-1)+(b-2)≦1.0, and preferably 0≦(a-1)≦0.9, 0≦(a-2)≦0.9, 0.1≦(a-1)+(a-2)≦0.9, 0≦(b-1)≦0.9, 0≦(b-2)≦0.9, 0.1≦(b-1)+(b-2)≦0.9, and 0.6≦(a-1)+(a-2)+(b-1)+(b-2)≦1.0.

The additional recurring units “c” and “d” may be present in the range: 0≦c≦0.8, more specifically 0≦c≦0.7, and 0≦d≦0.8, more specifically 0≦d≦0.7, provided that (a-1)+(a-2)+(b-1)+(b-2)+c+d=1.

It is noted that the meaning of (a-1)+(a-2)+(b-1)+(b-2)=1 is that in a polymer comprising recurring units (a-1), (a-2), (b-1), and (b-2), the sum of recurring units (a-1), (a-2), (b-1) and (b-2) is 100 mol % based on the total amount of entire recurring units. The meaning of (a-1)+(a-2)+(b-1)+(b-2)<1 is that the sum of recurring units (a-1), (a-2), (b-1), and (b-2) is less than 100 mol % based on the total amount of entire recurring units, indicating the inclusion of other recurring units.

In the resist composition of the invention, the polymeric surfactant(s) of formula (1) may be compounded in a total amount of 0.01 to 50 parts by weight, and preferably 0.1 to 10 parts by weight per 100 parts by weight of the base resin. At least 0.01 phr of the polymer is effective in improving the receding contact angle with water of the photoresist film at its surface. Up to 50 phr of the polymer is effective in forming a photoresist film having a low rate of dissolution in an alkaline developer and capable of maintaining the height of a fine pattern formed therein.

The resist composition of the invention is advantageously used as a chemically amplified positive or negative resist composition. In addition to the polymeric surfactant described above, the chemically amplified positive resist composition generally comprises at least a base resin, specifically a base resin comprising recurring units having acid labile groups and recurring units having hydroxy groups and/or adhesive groups of lactone ring.

Since the base resin includes recurring units having hydroxy groups and/or adhesive groups of lactone ring, the chemically amplified positive resist composition ensures tight adhesion to a substrate. Since the base resin includes recurring units having acid labile groups, the acid labile groups are deprotected with the acid generated by the acid generator during exposure so that the exposed area of resist is converted to be soluble in a developer, ensuring that a pattern is formed at a very high precision.

Base Resin

Suitable base resins include, but are not limited to, those polymers comprising units of the following formula (R1) and/or (R2) and having a weight average molecular weight (Mw) of about 1,000 to about 100,000, especially about 3,000 to about 30,000, as measured by GPC versus polystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or —CH₂CO₂R⁰⁰³.

R⁰⁰² is hydrogen, methyl or —CO₂R⁰⁰³.

R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-utyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl, butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl; ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent C₁-C₁₅ hydrocarbon group having at least one of fluorinated substituent groups, carboxyl groups and hydroxyl groups, for example, hydrogen, carboxyethyl, carboxybutyl, carboxycyclopentyl, carboxycyclohexyl, carboxynorbornyl, carboxyadamantyl, hydroxyethyl, hydroxybutyl, hydroxycyclopentyl, hydroxycyclohexyl, hydroxynorbornyl, hydroxyadamantyl, hydroxyhexafluoroisopropylcyclohexyl, and di(hydroxyhexafluoroisopropyl)cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent C₁-C₁₅ hydrocarbon group having at least one of fluorinated substituent groups, carboxyl groups and hydroxyl groups while the remaining R's independently represent hydrogen or straight, branched or cyclic C₁-C₁₅ alkyl groups. Examples of the monovalent C₁-C₁₅ hydrocarbon group having at least one of fluorinated substituent groups, carboxyl groups and hydroxyl groups include carboxy, carboxymethyl, carboxyethyl, carboxybutyl, hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl, 4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl, 4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl, carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl, carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl, hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl, hydroxyadamantyloxycarbonyl, hydroxyhexafluoroisopropylcyclohexyloxycarbonyl, and di(hydroxyhexafluoroisopropyl)cyclohexyloxycarbonyl. Examples of the straight, branched or cyclic C₁-C₁₅ alkyl group are the same as exemplified for R⁰⁰³.

Alternatively, two of R⁰⁰⁵ to R⁰⁰⁸ (e.g., R⁰⁰⁵ and R⁰⁰⁶, or R⁰⁰⁶ and R⁰⁰⁷) may bond together to form a ring with the carbon atom(s) to which they are attached. In that event, at least one of ring-forming R⁰⁰⁵ to R⁰⁰⁸ is a divalent C₁-C₁₅ hydrocarbon group having a fluorinated substituent group and/or carboxyl group or hydroxyl group, while the remaining are independently a single bond or a straight, branched or cyclic C₁-C₁₅ alkylene group. Examples of the divalent C₁-C₁₅ hydrocarbon group having a fluorinated substituent group and/or carboxyl group or hydroxyl group include the groups exemplified as the monovalent hydrocarbon group having a fluorinated substituent group and/or carboxyl group or hydroxyl group, with one hydrogen atom eliminated therefrom. Examples of the straight, branched or cyclic C₁-C₁₅ alkylene groups include the groups exemplified for R⁰⁰³, with one hydrogen atom eliminated therefrom.

R⁰⁰⁹ is a monovalent C₃-C₁₅ hydrocarbon group containing a —CO₂— partial structure, for example, 2-oxooxolan-3-yl, 4,4-dimethyl-2-oxooxolan-3-yl, 4-methyl-2-oxooxan-4-yl, 2-oxo-1,3-dioxolan-4-ylmethyl, and 5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent C₂-C₁₅ hydrocarbon group containing a —CO₂— partial structure, while the remaining R's are independently hydrogen or straight, branched or cyclic C₁-C₁₅ alkyl groups. Examples of the monovalent C₂-C₁₅ hydrocarbon group containing a —CO₂— partial structure include 2-oxooxolan-3-yloxycarbonyl, 4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl, 4-methyl-2-oxooxan-4-yloxycarbonyl, 2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and 5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branched or cyclic C₁-C₁₅ alkyl groups are the same as exemplified for R⁰⁰³.

Alternatively, two of R⁰¹⁰ to R⁰¹³ (e.g., R⁰¹⁰ and R⁰¹¹, or R⁰¹¹ and R⁰¹²) may bond together to form a ring with the carbon atom(s) to which they are attached. In that event, at least one of ring-forming R⁰¹⁰ to R⁰¹³ is a divalent C₁-C₁₅ hydrocarbon group containing a —CO₂— partial structure, while the remaining are independently a single bond or a straight, branched or cyclic C₁-C₁₅ alkylene group. Examples of the divalent C₁-C₁₅ hydrocarbon group containing a —CO₂— partial structure include 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl, 1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as well as the groups exemplified as the monovalent hydrocarbon group containing a —CO₂— partial structure, with one hydrogen atom eliminated therefrom. Examples of the straight, branched or cyclic C₁-C₁₅ alkylene groups include the groups exemplified for R⁰⁰³, with one hydrogen atom eliminated therefrom.

R⁰¹⁴ is a polycyclic C₇-C₁₅ hydrocarbon group or an alkyl group containing a polycyclic hydrocarbon group, for example, norbornyl, bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl, adamantyl, ethyladamantyl, butyladamantyl, norbornylmethyl, and adamantylmethyl.

R⁰¹⁵ is an acid labile group, which will be described later.

X is —CH₂ or an oxygen atom.

The subscript k is 0 or 1.

The acid labile groups represented by R⁰¹⁵ may be selected from a variety of such groups. Examples of the acid labile group are groups of the following general formulae is (L1) to (L4), tertiary alkyl groups of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilyl groups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms.

The broken line indicates a valence bond.

In formula (L1), R^(L01) and R^(L02) are hydrogen or straight, branched or cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Examples include hydrogen, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl, 2-ethylhexyl, n-octyl, and adamantyl. R^(L03) is a monovalent hydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may contain a hetero atom such as oxygen, examples of which include unsubstituted straight, branched or cyclic alkyl groups and straight, branched or cyclic alkyl groups in which some hydrogen atoms are replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like. Examples of the straight, branched or cyclic alkyl groups are as exemplified above for R^(L01) and R^(L02), and examples of the substituted alkyl groups are shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) and R^(L03) may bond together to form a ring with the carbon and oxygen atoms to which they are attached. Each of R^(L01), R^(L02) and R^(L03) is a straight or branched alkylene group of 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbon atoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in which each alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20 carbon atoms, or a group of formula (L1). Exemplary tertiary alkyl groups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl, 2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl, 1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, 2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and 5-methyl-2-oxooxolan-5-yl. In formula (L2), y is an integer of 0 to 6.

In formula (L3), R^(L05) is a substituted or unsubstituted, straight, branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstituted C₆-C₂₀ aryl group. Examples of the substituted or unsubstituted alkyl groups include straight, branched or cyclic ones such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl and bicyclo[2.2.1]heptyl; substituted forms of the foregoing in which some hydrogen atoms are replaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, sulfo or other groups; and substituted forms of the foregoing in which some of the methylene groups are replaced by oxygen or sulfur atoms. Exemplary substituted or unsubstituted aryl groups are phenyl, methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. In formula (L3), m is 0 or 1, n is 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.

In formula (L4), R^(L06) is a substituted or unsubstituted, straight, branched or cyclic C₁-C₁₀ alkyl group or a substituted or unsubstituted C₆-C₂₀ aryl group. Examples of these groups are the same as exemplified for R^(L05). R^(L07) to R^(L16) independently represent hydrogen or monovalent C₁-C₁₅ hydrocarbon groups. Exemplary hydrocarbon groups are straight, branched or cyclic alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl and cyclohexylbutyl, and substituted forms of the foregoing in which some hydrogen atoms are replaced by hydroxyl, alkoxy, carboxy, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio, sulfo or other groups. Alternatively, two of R^(L07) to R^(L16) may bond together to form a ring with the carbon atom to which they are attached (for example, a pair of R^(L07) and R^(L08), R^(L07) and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10), R^(L11) and R^(L12), R^(L13) and R^(L14), or a similar pair form a ring). Each of R^(L07) to R^(L16) represents a divalent C₁-C₁₅ hydrocarbon group when they form a ring, examples of which are the ones exemplified above for the monovalent hydrocarbon groups, with one hydrogen atom being eliminated. Two of R^(L07) to R^(L16) which are attached to vicinal carbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) and R^(L15), R^(L13) and R^(L15), or a similar pair) may bond together directly to form a double bond.

Of the acid labile groups of formula (L1), the straight and branched ones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, for example, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl, tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) include tert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl, tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl, 1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl, 1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl, 1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl, 2-tetrahydropyranyloxycarbonylmethyl, and 2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include 1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl, 1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl, 1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl, 1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl, 1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl, 3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and 3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are preferably groups of the following formulae (L4-1) to (L4-4).

In formulae (L4-1) to (L4-4), the broken line indicates a bonding site and direction. R^(L41) is each independently selected from monovalent hydrocarbon groups, typically straight, branched or cyclic C₁-C₁₀ alkyl groups, for example, methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, and cyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers and diastereomers. Each of formulae (L4-1) to (L4-4) collectively represents all such stereoisomers. Such stereoisomers may be used alone or in admixture.

For example, the general formula (L4-3) represents one or a mixture of two selected from groups having the following general formulas (L4-3-1) and (L4-3-2).

Herein R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of two or more selected from groups having the following general formulas (L4-4-1) to (L4-4-4).

Herein R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1) to (L4-4-4) collectively represents an enantiomer thereof and a mixture of enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exo side relative to the bicyclo[2.2.1]heptane ring, which ensures high reactivity for acid catalyzed elimination reaction (see JP-A 2000-336121). In preparing these monomers having a tertiary exo-alkyl group of bicyclo[2.2.1]heptane skeleton as a substituent group, there may be contained monomers substituted with an endo-alkyl group as represented by the following formulas (L4-1-endo) to (L4-4-endo). For good reactivity, an exo proportion of at least 50 mol % is preferred, with an exo proportion of at least 80 mol % being more preferred.

Herein R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are given below.

Examples of the tertiary C₄-C₂₀ alkyl, tri(C₁-C₆-alkyl)silyl and C₄-C₂₀ oxoalkyl groups included in the acid labile groups represented by R⁰¹⁵ are as exemplified above for R^(L04).

In formula (R2), R⁰¹⁶ and R⁰¹⁸ each are hydrogen or methyl. R⁰¹⁷ is a straight, branched or cyclic C₁-C₈ alkyl group.

In formula (R1), the subscripts a1′, a2′, a3′, b1′, b2′, b3′, c1′, c2′, c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1, satisfying a1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1. In formula (R2), f′, g′, h′, i′, j′, k′, l′, and m′ are numbers from 0 to less than 1, satisfying f′+g′+h′+i′+j′+k′+l′+m′=1; x′, y′ and z′ are each an integer of 0 to 3, satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3. In addition, one or more monomers selected from indenes, norbornadienes, acenaphthylenes and vinyl ethers may be copolymerized.

Examples of the recurring units incorporated at compositional ratio a1′ in formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′ in formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′ in formula (R1) are shown below, though not limited thereto.

Examples of polymers comprising recurring units in compositional ratios a3′, b3′, c3′ and d3′ in formula (R1) are shown below, though not limited thereto.

Furthermore, recurring units having a photosensitive sulfonium salt as represented by the general formula (PA) may be copolymerized with (R1) and/or (R2) and incorporated in the polymers.

Herein R^(p1) is hydrogen or methyl. R^(p2) is a phenylene group, —O—R^(p5)— or —C(═O)—X—R^(p5)— wherein X is an oxygen atom or NH, and R^(p5) is a straight, branched or cyclic C₁-C₆ alkylene, alkenylene or phenylene group which may contain a carbonyl, ester or ether group. R^(p3) and R^(p4) are each independently a straight, branched or cyclic C₁-C₁₂ alkyl group which may contain a carbonyl, ester or ether group, or a C₆-C₁₂ aryl group, C₇-C₂₀ aralkyl group or thiophenyl group. X⁻ is a non-nucleophilic counter ion.

The polymer used as the base resin is not limited to one type and a mixture of two or more polymers may be added. The use of plural polymers allows for easy adjustment of resist properties.

Acid Generator

In the resist composition of the invention, an acid generator, specifically a compound capable of generating an acid in response to actinic light or radiation may be included in order that the resist composition function as a chemically amplified positive resist composition. The acid generator may be any compound capable of generating an acid upon exposure of high-energy radiation, which is generally referred to as “photoacid generator” or PAG. Suitable photoacid generators include sulfonium salts, iodonium salts, sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acid generators. Exemplary acid generators are given below while they may be used alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates, bis(substituted alkylsulfonyl)imides and tris(substituted alkylsulfonyl)methides. Exemplary sulfonium cations include triphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium, bis(4-tert-butoxyphenyl)phenylsulfonium, tris(4-tert-butoxyphenyl)sulfonium, (3-tert-butoxyphenyl)diphenylsulfonium, bis(3-tert-butoxyphenyl)phenylsulfonium, tris(3-tert-butoxyphenyl)sulfonium, (3,4-di-tert-butoxyphenyl)diphenylsulfonium, bis(3,4-di-tert-butoxyphenyl)phenylsulfonium, tris(3,4-di-tert-butoxyphenyl)sulfonium, diphenyl(4-thiophenoxyphenyl)sulfonium, (4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium, tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium, (4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium, tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium, dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium, 4-methoxyphenyldimethylsulfonium, trimethylsulfonium, 2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium, tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium, 2-oxo-2-phenylethylthiacyclopentanium, 4-n-butoxynaphthyl-1-thiacyclopentanium, and 2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, 4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate, 2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate, 2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate, 2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate, 1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Exemplary bis(substituted alkylsulfonyl)imides include bistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide, bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. A typical tris(substituted alkylsulfonyl)methide is tristrifluoromethylsulfonylmethide. Sulfonium salts based on combination of the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates, bis(substituted alkylsulfonyl)imides and tris(substituted alkylsulfonyl)methides. Exemplary iodonium cations are aryliodonium cations including diphenyliodonium, bis(4-tert-butylphenyl)iodonium, 4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, 4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate, 2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate, 2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate, 2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate, 1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Exemplary bis(substituted alkylsulfonyl)imides include bistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide, bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. A typical tris(substituted alkylsulfonyl)methide is tristrifluoromethylsulfonylmethide. Iodonium salts based on combination of the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethane compounds and sulfonyl-carbonyldiazomethane compounds such as

-   bis(ethylsulfonyl)diazomethane, -   bis(1-methylpropylsulfonyl)diazomethane, -   bis(2-methylpropylsulfonyl)diazomethane, -   bis(1,1-dimethylethylsulfonyl)diazomethane, -   bis(cyclohexylsulfonyl)diazomethane, -   bis(perfluoroisopropylsulfonyl)diazomethane, -   bis(phenylsulfonyl)diazomethane, -   bis(4-methylphenylsulfonyl)diazomethane, -   bis(2,4-dimethylphenylsulfonyl)diazomethane, -   bis(2-naphthylsulfonyl)diazomethane, -   bis(4-acetyloxyphenylsulfonyl)diazomethane, -   bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane, -   bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane, -   bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   4-methylphenylsulfonylbenzoyldiazomethane, -   tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane, -   2-naphthylsulfonylbenzoyldiazomethane, -   4-methylphenylsulfonyl-2-naphthoyldiazomethane, -   methylsulfonylbenzoyldiazomethane, and -   tert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imide skeletons with sulfonates. Exemplary imide skeletons are succinimide, naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylic acid imide, 5-norbornene-2,3-dicarboxylic acid imide, and 7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplary sulfonates include trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, mesitylenesulfonate, 2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate, 2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate, 2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate, 2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate, 1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2.5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoin mesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol, phloroglucinol, catechol, resorcinol, and hydroquinone, in which all the hydroxyl groups are substituted by trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate, 2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate, 2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate, 2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate, 1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzyl sulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate, with exemplary sulfonates including trifluoromethanesulfonate, pentafluoroethanesulfonate, nonafluorobutanesulfonate, dodecafluorohexanesulfonate, pentafluoroethylperfluorocyclohexanesulfonate, heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate, pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate, 4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate, naphthalenesulfonate, camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate, butanesulfonate, methanesulfonate, 2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate, 1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate, 2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate, 2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate, 2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate, 1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate, 1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate, 1,1-difluoro-2-naphthyl-ethanesulfonate, 1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and 1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate. Also useful are analogous nitrobenzyl sulfonate compounds in which the nitro group on the benzyl side is substituted by a trifluoromethyl group.

Sulfone photoacid generators include

-   bis(phenylsulfonyl)methane, -   bis(4-methylphenylsulfonyl)methane, -   bis(2-naphthylsulfonyl)methane, -   2,2-bis(phenylsulfonyl)propane, -   2,2-bis(4-methylphenylsulfonyl)propane, -   2,2-bis(2-naphthylsulfonyl)propane, -   2-methyl-2-(p-toluenesulfonyl)propiophenone, -   2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and -   2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are described in Japanese Patent No. 2,906,999 and JP-A 9-301948 and include

-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime, -   bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime, -   bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime, -   bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime, -   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime, -   bis-O-(n-butanesulfonyl)-α-diphenylglyoxime, -   bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime, -   bis-O-(methanesulfonyl)-α-dimethylglyoxime, -   bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime, -   bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime, -   bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime, -   bis-O-(benzenesulfonyl)-α-dimethylglyoxime, -   bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime, -   bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime, -   bis-O-(xylenesulfonyl)-α-dimethylglyoxime, -   bis-O-(trifluoromethanesulfonyl)-nioxime, -   bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime, -   bis-O-(10-camphorsulfonyl)-nioxime, -   bis-O-(benzenesulfonyl)-nioxime, -   bis-O-(p-fluorobenzenesulfonyl)-nioxime, -   bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, and -   bis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No. 6,004,724, for example, (5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile, (5-(O-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile, (5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenylacetonitrile, (5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile (5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile, (5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methyl-phenyl)acetonitrile, etc. Also included are the oxime sulfonates described in U.S. Pat. No. 6,916,591, for example, (5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile and (5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No. 6,261,738 and JP-A 2000-314956, for example, 2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate); 2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate); 2,2,2-trifluoro-1-phenylethanone oxime-O-(2-naphthylsulfonate); 2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2,4,6-trimethylphenylsulfonate); 2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate); 2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone oxime-O-(1-naphthylsulfonate); 2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone oxime-O-(2-naphthylsulfonate); 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(1-naphthylsulfonate); 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(2-naphthylsulfonate); 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanone oxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanone oxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanone oxime-O-(2,4,6-trimethylphenyl)sulfonate; 2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methyl-sulfonate; 2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone oxime-O-(1-naphthyl)sulfonate; 2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanone oxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(1-naphthyl)sulfonate; 2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanone oxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-(4-methylphenyl)sulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-(4-dodecylphenyl)-sulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate; 2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-(4-dodecylphenyl)sulfonate; 2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-octylsulfonate; 2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate; 2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanone oxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanone oxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanone oxime-O-propylsulfonate; 1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoroethanone oxime-O-sulfonyl]phenyl; 2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-methylcarbonyloxy-phenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxyphenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanone oxime-O-propylsulfonate; 2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanone oxime(trifluoromethanesulfonate); 2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanone oxime(1-propanesulfonate); and 2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)-ethanone oxime(1-butanesulfonate). Also included are the oxime sulfonates described in U.S. Pat. No. 6,916,591, for example, 2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanone oxime(4-(4-methylphenylsulfonyloxy)-phenylsulfonate) and 2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanone oxime(2,5-bis(4-methylphenylsulfonyloxy)-benzenesulfonyloxy)phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 and JP-A 9-230588 and the references cited therein, for example,

-   α-(p-toluenesulfonyloxyimino)-phenylacetonitrile, -   α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile, -   α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile, -   α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile, -   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile, -   α-(benzenesulfonyloxyimino)-2-thienylacetonitrile, -   α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile, -   α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile, -   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile, -   α-(tosyloxyimino)-3-thienylacetonitrile, -   α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, and -   α-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the formula:

wherein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl or halobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkyl group of 1 to 11 carbon atoms, and Ar^(s1) is substituted or unsubstituted aromatic or hetero-aromatic group, as described in WO 2004/074242.

Examples include

-   2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene, -   2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene, -   2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene, -   2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-4-biphenyl, -   2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-4-biphenyl,     and -   2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554, for example,

-   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile, -   bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,     etc.

Of these, preferred photoacid generators are sulfonium salts, bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates and glyoxime derivatives. More preferred photoacid generators are sulfonium salts, bissulfonyldiazomethanes, N-sulfonyloxyimides, and oxime-O-sulfonates. Typical examples include

-   triphenylsulfonium p-toluenesulfonate, -   triphenylsulfonium camphorsulfonate, -   triphenylsulfonium pentafluorobenzenesulfonate, -   triphenylsulfonium nonafluorobutanesulfonate, -   triphenylsulfonium 4-(4′-toluenesulfonyloxy)benzenesulfonate, -   triphenylsulfonium 2,4,6-triisopropylbenzenesulfonate, -   4-tert-butoxyphenyldiphenylsulfonium p-toluenesulfonate, -   4-tert-butoxyphenyldiphenylsulfonium camphorsulfonate, -   4-tert-butoxyphenyldiphenylsulfonium     4-(4′-toluenesulfonyloxy)benzenesulfonate, -   tris(4-methylphenyl)sulfonium camphorsulfonate, -   tris(4-tert-butylphenyl)sulfonium camphorsulfonate, -   4-tert-butylphenyldiphenylsulfonium camphorsulfonate, -   4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butanesulfonate, -   4-tert-butylphenyldiphenylsulfonium     pentafluoroethyl-perfluorocyclohexanesulfonate, -   4-tert-butylphenyldiphenylsulfonium perfluoro-1-octanesulfonate, -   triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate, -   triphenylsulfonium     1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate, -   bis(tert-butylsulfonyl)diazomethane, -   bis(cyclohexylsulfonyl)diazomethane, -   bis(2,4-dimethylphenylsulfonyl)diazomethane, -   bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane, -   bis(4-tert-butylphenylsulfonyl)diazomethane, -   N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide, -   N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide, -   2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene, -   2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,     and -   2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene.

In the chemically amplified resist composition, an appropriate amount of the photoacid generator is, but not limited to, 0.1 to 20 parts, and especially 0.1 to 10 parts by weight per 100 parts by weight of the base resin. If the amount of the PAG is up to 20 phr, the resulting photoresist film has a sufficiently high transmittance to minimize a risk of degrading resolution. The PAG may be used alone or in admixture of two or more. The transmittance of the resist film can be controlled by using a PAG having a low transmittance at the exposure wavelength and adjusting the amount of the PAG added.

In the resist composition, there may be added a compound which is decomposed with an acid to generate another acid, that is, acid-amplifier compound. For these compounds, reference should be made to J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9, 29-30 (1996).

Examples of the acid-amplifier compound include tert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and 2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto. Of well-known photoacid generators, many of those compounds having poor stability, especially poor thermal stability exhibit an acid amplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifier compound is up to 2 parts, and preferably up to 1 part by weight per 100 parts by weight of the base resin. Up to 2 phr of the acid-amplifier compound allows for diffusion control, minimizing a risk of degrading resolution and pattern profile.

In addition to the base resin and PAG as well as the polymeric surfactant, the resist composition of the invention may further comprise at least one of an organic solvent, a basic compound, a dissolution regulator, a crosslinker, and a surfactant.

Solvent

The organic solvent used herein may be any organic solvent in which the base resin, acid generator, and other components are soluble. Illustrative, non-limiting, examples of the organic solvent include ketones such as cyclohexanone and methyl-2-n-amyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; esters such as propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate; and lactones such as γ-butyrolactone. These solvents may be used alone or in combinations of two or more thereof. Of the above organic solvents, it is recommended to use diethylene glycol dimethyl ether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate, and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000 parts, especially about 400 to 2,500 parts by weight per 100 parts by weight of the base resin.

Basic Compound

In the resist composition, an organic nitrogen-containing compound or compounds may be compounded as the basic compound. The organic nitrogen-containing compound used herein is preferably a compound capable of suppressing the rate of diffusion when the acid generated by the acid generator diffuses within the resist film. The inclusion of organic nitrogen-containing compound holds down the rate of acid diffusion within the resist film, resulting in better resolution. In addition, it suppresses changes in sensitivity following exposure and reduces substrate and environment dependence, as well as improving the exposure latitude and the pattern profile.

Suitable organic nitrogen-containing compounds include primary, secondary, and tertiary aliphatic amines, mixed amines, aromatic amines, heterocyclic amines, nitrogen-containing compounds having carboxyl group, nitrogen-containing compounds having sulfonyl group, nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, alcoholic nitrogen-containing compounds, amide derivatives, imide derivatives, and carbamate derivatives.

Examples of suitable primary aliphatic amines include ammonia, methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, dodecylamine, cetylamine, methylenediamine, ethylenediamine, and tetraethylenepentamine. Examples of suitable secondary aliphatic amines include dimethylamine, diethylamine, di-n-propylamine, diisopropylamine, di-n-butylamine, diisobutylamine, di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine, N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, and N,N-dimethyltetraethylenepentamine. Examples of suitable tertiary aliphatic amines include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, triisobutylamine, tri-sec-butylamine, tripentylamine, tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, tridodecylamine, tricetylamine, N,N,N′,N′-tetramethylmethylenediamine, N,N,N′,N′-tetramethylethylenediamine, and N,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine, methylethylpropylamine, benzylamine, phenethylamine, and benzyldimethylamine. Examples of suitable aromatic and heterocyclic amines include aniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, ethylaniline, propylaniline, trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene, pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazole derivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g., thiazole and isothiazole), imidazole derivatives (e.g., imidazole, 4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives, pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives, imidazolidine derivatives, pyridine derivatives (e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine, butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine, triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine, 4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives, piperidine derivatives, piperazine derivatives, morpholine derivatives, indole derivatives, isoindole derivatives, 1H-indazole derivatives, indoline derivatives, quinoline derivatives (e.g., quinoline and 3-quinolinecarbonitrile), isoquinoline derivatives, cinnoline derivatives, quinazoline derivatives, quinoxaline derivatives, phthalazine derivatives, purine derivatives, pteridine derivatives, carbazole derivatives, phenanthridine derivatives, acridine derivatives, phenazine derivatives, 1,10-phenanthroline derivatives, adenine derivatives, adenosine derivatives, guanine derivatives, guanosine derivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl group include aminobenzoic acid, indolecarboxylic acid, and amino acid derivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid, glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine, methionine, phenylalanine, threonine, lysine, 3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples of suitable nitrogen-containing compounds having sulfonyl group include 3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples of suitable nitrogen-containing compounds having hydroxyl group, nitrogen-containing compounds having hydroxyphenyl group, and alcoholic nitrogen-containing compounds include 2-hydroxypyridine, aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine, diethanolamine, triethanolamine, N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine, 1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide. Examples of suitable amide derivatives include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, benzamide, and 1-cyclohexylpyrrolidone. Suitable imide derivatives include phthalimide, succinimide, and maleimide. Suitable carbamate derivatives include N-t-butoxycarbonyl-N,N-dicyclohexylamine, N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the following general formula (B)-1 may also be included alone or in admixture. N(X)_(n)(Y)_(3-n)  (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independently hydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which may contain an ether or hydroxyl group; and side chain X is independently selected from groups of the following general formulas (X1) to (X3), and two or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight or branched C₁-C₄ alkylene groups; R³⁰¹ and R³⁰⁴ are independently hydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group which may contain at least one hydroxyl, ether, ester group or lactone ring; R³⁰³ is a single bond or a straight or branched C₁-C₄ alkylene group; and R³⁰⁶ is a straight, branched or cyclic C₁-C₂₀ alkyl group which may contain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl)amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris(2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine, tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine, 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane, 4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane, 1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6, tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine, N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine, tris(2-methoxycarbonyloxyethyl)amine, tris(2-tert-butoxycarbonyloxyethyl)amine, tris[2-(2-oxopropoxy)ethyl]amine, tris[2-(methoxycarbonylmethyl)oxyethyl]amine, tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine, tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine, tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine, N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine, N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine, N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine, N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine, N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine, N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)ethylamine, N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)ethylamine, N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine, N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine, N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(methoxycarbonyl)ethyl]amine, N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine, N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine, N-methyl-bis(2-pivaloyloxyethyl)amine, N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine, N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine, tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine, N-butyl-bis(methoxycarbonylmethyl)amine, N-hexyl-bis(methoxycarbonylmethyl)amine, and β-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds having cyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branched C₂-C₂₀ alkylene group which may contain one or more carbonyl, ether, ester or sulfide groups.

Illustrative examples of the organic nitrogen-containing compounds having formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine, 1-[2-(methoxymethoxy)ethyl]piperidine, 4-[2-(methoxymethoxy)ethyl]morpholine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine, 1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine, 4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate, 2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethyl methoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine, 1-[2-(t-butoxycarbonyloxy)ethyl]piperidine, 4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl 3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl 3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl 2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate, methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl 3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate, 2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate, tetrahydrofurfuryl 3-morpholinopropionate, glycidyl 3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate, 2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl 3-morpholinopropionate, cyclohexyl 3-piperidinopropionate, α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methyl piperidinoacetate, methyl morpholinoacetate, methyl thiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethyl morpholinoacetate 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl 2-(2-methoxyethoxy)acetate, 2-morpholinoethyl 2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate, 2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate, 2-morpholinoethyl laurate, 2-morpholinoethyl myristate, 2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyano group represented by the following general formulae (B)-3 to (B)-6 may be blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are each independently a straight or branched C₁-C₄ alkylene group.

Illustrative examples of the organic nitrogen-containing compounds having cyano represented by formulae (B)-3 to (B)-6 include 3-(diethylamino)propiononitrile, N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile, N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile, N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile, N,N-bis(2-methoxyethyl)-3-aminopropiononitrile, N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate, N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile, N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile, N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile, N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile, N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile, N,N-bis(2-hydroxyethyl)aminoacetonitrile, N,N-bis(2-acetoxyethyl)aminoacetonitrile, N,N-bis(2-formyloxyethyl)aminoacetonitrile, N,N-bis(2-methoxyethyl)aminoacetonitrile, N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate, N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile, N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile, N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile, N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile, N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile, N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile, N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile, N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile, 1-piperidinepropiononitrile, 4-morpholinepropiononitrile, 1-pyrrolidineacetonitrile, 1-piperidineacetonitrile, 4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate, cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl 3-diethylaminopropionate, 2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl 1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl 4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate, 2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl 4-morpholinepropionate.

Also included are organic nitrogen-containing compounds having an imidazole structure and a polar functional group, represented by the general formula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar functional group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group, aryl group or aralkyl group having 1 to 10 carbon atoms.

Also included are organic nitrogen-containing compounds having a benzimidazole structure and a polar functional group, represented by the general formula (B)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic alkyl group, aryl group or aralkyl group having 1 to 10 carbon atoms. R³¹⁵ is a polar functional group-bearing, straight, branched or cyclic C₁-C₂₀ alkyl group, and the alkyl group contains as the polar functional group at least one group selected from among ester, acetal and cyano groups, and may additionally contain at least one group selected from among hydroxyl, carbonyl, ether, sulfide and carbonate groups.

Further included are heterocyclic nitrogen-containing compounds having a polar functional group, represented by the general formulae (B)-9 and (B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or ≡C—R³²³, R³¹⁶ is a straight, branched or cyclic alkyl group of 2 to 20 carbon atoms bearing at least one polar functional group selected from among hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano and acetal groups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms, or a pair of R³¹⁷ and R³¹⁸ and a pair of R³¹⁹ and R³²⁰, taken together, may form a benzene, naphthalene or pyridine ring; R³²¹ is a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms; R³²² and R³²³ each are a hydrogen atom, a straight, branched or cyclic alkyl group or aryl group having 1 to 10 carbon atoms, or a pair of R³²¹ and R³²³, taken together, may form a benzene or naphthalene ring.

Also included are organic nitrogen-containing compounds of aromatic carboxylic ester structure having the general formulae (B)-11 to (B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, in which some or all of hydrogen atoms may be replaced by halogen atoms, straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups, C₇-C₂₀ aralkyl groups, C₂-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups or C₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ is a C₁-C₁₀ alkyl group, in which some methylene groups may be replaced by oxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which some methylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond, methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is 0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is a nitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogen atom or CR³³². R³³⁰, R³³¹ and R³³⁰ are each independently hydrogen, methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair of R³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀ hetero-aromatic ring.

Further included are organic nitrogen-containing compounds of 7-oxanorbornane-2-carboxylic ester structure having the general formula (B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkyl group. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀ aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polar functional groups selected from among ether, carbonyl, ester, alcohol, sulfide, nitrile, amine, imine, and amide and in which some hydrogen atoms may be replaced by halogen atoms. R³³⁴ and R³³⁵, taken together, may form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atoms.

The organic nitrogen-containing compounds may be used alone or in admixture of two or more. The organic nitrogen-containing compound is preferably formulated in an amount of 0.001 to 2 parts, and especially 0.01 to 1 part by weight, per 100 parts by weight of the base resin. At least 0.001 phr of the nitrogen-containing compound achieves a desired addition effect whereas up to 2 phr minimizes a risk of lowering sensitivity.

If desired, the resist composition of the invention may include a surfactant which is commonly used for improving the coating characteristics. It may be added in conventional amounts so long as this does not compromise the objects of the invention.

Nonionic surfactants are preferred, examples of which include perfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters, perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, and fluorinated organosiloxane compounds. Useful surfactants are commercially available under the trade names Fluorad FC-430 and FC-431 from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30 and KH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, US-403 and DS-451 from Daikin Industry Co., Ltd., Megaface F-8151 from Dai-Nippon Ink & Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co., Ltd. Preferred surfactants are Fluorad FC-430 from Sumitomo 3M, Ltd., KH-20 and KH-30 from Asahi Glass Co., Ltd., and X-70-093 from Shin-Etsu Chemical Co., Ltd.

Also, if desired, other components including dissolution regulators, carboxylic acid compounds and acetylene alcohol derivatives may be added to the resist composition of the invention. Optional components may be added in conventional amounts so long as this does not compromise the objects of the invention.

Dissolution Regulator

The dissolution regulator which can be added to the resist composition is a compound having on the molecule at least two phenolic hydroxyl groups, in which an average of from 0 to 100 mol % of all the hydrogen atoms on the phenolic hydroxyl groups are replaced by acid labile groups or a compound having on the molecule at least one carboxyl group, in which an average of 50 to 100 mol % of all the hydrogen atoms on the carboxyl groups are replaced by acid labile groups, both the compounds having a weight average molecular weight within a range of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolic hydroxyl groups with acid labile groups is on average at least 0 mol %, and preferably at least 30 mol %, of all the phenolic hydroxyl groups. The upper limit is 100 mol %, and preferably 80 mol %. The degree of substitution of the hydrogen atoms on the carboxyl groups with acid labile groups is on average at least 50 mol %, and preferably at least 70 mol %, of all the carboxyl groups, with the upper limit being 100 mol %.

Preferable examples of such compounds having two or more phenolic hydroxyl groups or compounds having at least one carboxyl group include those of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight or branched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl, ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₁₀ alkyl or alkenyl group, or —(R²⁰⁷ h-COOH wherein R²⁰⁷ is a straight or branched C₁-C₁₀ alkylene and h is 0 or 1, for example, those exemplified for R²⁰¹ and R²⁰² and —COOH and —CH₂COOH.

R²⁰⁴ is —(CH₂)_(i)— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom, for example, ethylene, phenylene, carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom, for example, methylene and those exemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group, or a phenyl or naphthyl group having hydroxyl substituted thereon, for example, hydrogen, methyl, ethyl, butyl, propyl, ethynyl, cyclohexyl, hydroxyl-substituted phenyl, and hydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t, s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, and s″+t″=4, and are such that each phenyl skeleton has at least one hydroxyl group; and α is a number such that the compounds of formula (D8) or (D9) have a weight average molecular weight of from 100 to 1,000.

Exemplary acid labile groups on the dissolution regulator include a variety of such groups, typically groups of the general formulae (L1) to (L4), tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilyl groups in which each of the alkyls has 1 to 6 carbon atoms, and oxoalkyl groups of 4 to 20 carbon atoms. Examples of the respective groups are as previously described.

The dissolution regulator may be formulated in an amount of 0 to 50 parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts by weight, per 100 parts by weight of the base resin, and may be used singly or as a mixture of two or more thereof. Up to 50 phr of the dissolution regulator minimizes a risk of slimming the patterned film and reducing the resolution.

The dissolution regulator can be synthesized by introducing acid labile groups into a compound having phenolic hydroxyl or carboxyl groups in accordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended. Exemplary, non-limiting carboxylic acid compounds include one or more compounds selected from Groups I and II below. Including this compound improves the PED stability of the resist and ameliorates edge roughness on nitride film substrates.

Group I:

Compounds in which some or all of the hydrogen atoms on the phenolic hydroxyl groups of the compounds of general formulas (A1) to (A10) below are replaced by —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branched alkylene of 1 to 10 carbon atoms), and in which the molar ratio C/(C+D) of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in the molecule is from 0.1 to 1.0.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight or branched C₁-C₈ alkyl or alkenyl; R⁴⁰⁴ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogen or —R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), a C₁-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁶ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or a hydroxyl-substituted phenyl or naphthyl; R⁴⁰⁸ is hydrogen or methyl; R⁴⁰⁹ is a straight or branched C₁-C₁₀ alkylene; R⁴¹⁰ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or a —R⁴¹¹—COOH group; R⁴¹¹ is a straight or branched C₁-C₁₀ alkylene; the letter j is an integer from 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4 are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4=6, and are such that each phenyl structure has at least one hydroxyl group; u is a number from 1 to 4, h is a number from 1 to 4; κ is a number such that the compound of formula (A6) may have a weight average molecular weight of 1,000 to 5,000; and λ is a number such that the compound of formula (A7) may have a weight average molecular weight of 1,000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² is hydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0, and s5+t5=5; and h is a number from 1 to 4.

Illustrative, non-limiting examples of the compound having a carboxyl group include compounds of the general formulas AI-1 to AI-14 and AII-1 to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the —CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κ and λ are as defined above.

The compound having a ≡C—COOH group in the molecule is added in an amount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, more preferably 0.1 to 3 parts, even more preferably 0.1 to 2 parts by weight, per 100 parts by weight of the base resin. Up to 5 phr of the compound minimizes a risk of the resist composition reducing its resolution.

The resist composition of the invention may additionally include an acetylene alcohol derivative. Preferred acetylene alcohol derivatives are those having the general formula (S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or a straight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or a positive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol 61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol 104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol 485 from Air Products and Chemicals Inc., and Surfynol E1004 from Nisshin Chemical Industry K.K.

The acetylene alcohol derivative is preferably added in an amount of 0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, based on the weight of the resist composition. At least 0.01 wt % is fully effective in improving the coating operation and shelf stability. Up to 2 wt % minimizes a risk of the resist composition reducing its resolution.

Crosslinker

To the resist composition, any of crosslinkers which are commonly used in negative resist compositions may be added if desired. Typical crosslinkers are compounds having at least two hydroxymethyl, alkoxymethyl, epoxy or vinyl ether groups in a molecule. Substituted glycoluril derivatives, urea derivatives, and hexa(methoxymethyl)melamine compounds are suitable.

Examples include N,N,N′,N′-tetramethoxymethylurea, hexamethoxymethylmelamine, tetraalkoxymethyl-substituted glycoluril compounds such as tetrahydroxymethyl-substituted glycoluril and tetramethoxymethylglycoluril, and condensates of phenolic compounds such as substituted or unsubstituted bis(hydroxymethylphenol) compounds and bisphenol A with epichlorohydrin. Especially preferred crosslinkers include 1,3,4,6-tetraalkoxymethylglycolurils such as 1,3,4,6-tetramethoxymethylglycoluril, as well as 1,3,4,6-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol, 2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A, 1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea, and hexamethoxymethylmelamine.

An appropriate amount of the crosslinker is, but not limited thereto, 1 to 25 parts, and especially 5 to 20 parts by weight per 100 parts by weight of the base resin in the resist composition. The crosslinkers may be used alone or in admixture of any.

Protective Coating

The resist composition of the invention may be used in a pattern forming process adopting the immersion lithography. In the immersion lithography, a protective layer is formed on a photoresist layer, and a liquid is held between the protective layer and a projection lens. That is, the protective layer intervenes between the photoresist layer and the liquid. The protective layer is preferably an alkali-soluble protective layer based on a polymer having α-trifluoromethylalcohol groups as the alkali-soluble group. The polymers having α-trifluoromethylalcohol groups may be obtained through polymerization of monomers similar to the monomers from which recurring units (b-1) in formula (1) are derived. Also, monomers similar to the monomers from which recurring units (b-2) in formula (1) are derived may be copolymerized for preventing water penetration and/or improving a receding contact angle. Moreover, monomers having alkali-soluble groups in the form of α-trifluoromethylalcohol groups as shown below may be polymerized.

Also, monomers having a water repellent group may be polymerized, examples of which are shown below.

Provided that A stands for a proportion of a monomer having a α-trifluoromethylalcohol group, B stands for a proportion of a monomer similar to the monomers from which recurring units (b-2) are derived, C stands for a proportion of a monomer having a water repellent group, and A+B+C=100 mol %, these monomers are preferably (copolymerized in such proportions that A is in the range of 10 to 100 mol %, more specifically 30 to 100 mol %, B is in the range of 0 to 90 mol %, more specifically 0 to 70 mol %, C is in the range of 0 to 90 mol %, more specifically 0 to 70 mol %. The polymer thus obtained is preferred as a protective coating material.

The protective coating should preferably have an alkali dissolution rate of at least 50 nm/sec, and more preferably at least 100 nm/sec, as measured in an aqueous solution of 2.38 wt % tetramethylammonium hydroxide. The polymer for the protective coating should preferably have a weight average molecular weight of 1,000 to 100,000.

The solvent used for protective coating is not particularly limited although those solvents in which resist layers can be dissolved should be avoided. It is recommended to avoid the use of conventional resist solvents, for example, ketones such as cyclohexanone and methyl-2-n-amylketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; and esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate.

Suitable solvents in which resist layers are not dissolvable include nonpolar solvents, for example, higher alcohols of at least 4 carbon atoms, toluene, xylene, anisole, hexane, cyclohexane and ethers. Of these, higher alcohols of at least 4 carbon atoms are most desirable. Examples of suitable solvents include, but are not limited to, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, tert-amyl alcohol, neopentyl alcohol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-methyl-3-pentanol, cyclopentanol, 1-hexanol, 2-hexanol, 3-hexanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol, 4-methyl-2-pentanol, 4-methyl-3-pentanol, and cyclohexanol as well as diisopropyl ether, diisobutyl ether, diisopentyl ether, di-n-pentyl ether, methylcyclopentyl ether, and methylcyclohexyl ether. These solvents may be used alone or in admixture.

Fluorinated solvents are also preferred because resist layers are not dissolvable therein. Examples include, but are not limited to, 2-fluoroanisole, 3-fluoroanisole, 4-fluoroanisole, 2,3-difluoroanisole, 2,4-difluoroanisole, 2,5-difluoroanisole, 5,8-difluoro-1,4-benzodioxane, 2,3-difluorobenzyl alcohol, 1,3-difluoro-2-propanol, 2′,4′-difluoropropiophenone, 2,4-difluorotoluene, trifluoroacetaldehyde ethyl hemiacetal, trifluoroacetamide, trifluoroethanol, 2,2,2-trifluoroethyl butyrate, ethyl heptafluorobutyrate, ethyl heptafluorobutylacetate, ethyl hexafluoroglutarylmethyl, ethyl 3-hydroxy-4,4,4-trifluorobutyrate, ethyl 2-methyl-4,4,4-trifluoroacetoacetate, ethyl pentafluorobenzoate, ethyl pentafluoropropionate, ethyl pentafluoropropynylacetate, ethyl perfluorooctanoate, ethyl 4,4,4-trifluoroacetoacetate, ethyl 4,4,4-trifluorobutyrate, ethyl 4,4,4-trifluorocrotonate, ethyl trifluorosulfonate, ethyl 3-(trifluoromethyl)butyrate, ethyl trifluoropyruvate, S-ethyl trifluoroacetate, fluorocyclohexane, 2,2,3,3,4,4,4-heptafluoro-1-butanol, 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione, 1,1,1,3,5,5,5-heptafluoropentane-2,4-dione, 3,3,4,4,5,5,5-heptafluoro-2-pentanol, 3,3,4,4,5,5,5-heptafluoro-2-pentanone, isopropyl 4,4,4-trifluoroacetoacetate, methyl perfluorodecanoate, methyl perfluoro(2-methyl-3-oxahexanoate), methyl perfluorononanoate, methyl perfluorooctanoate, methyl 2,3,3,3-tetrafluoropropionate, methyl trifluoroacetoacetate, 1,1,1,2,2,6,6,6-octafluoro-2,4-hexanedione, 2,2,3,3,4,4,5,5-octafluoro-1-pentanol, 1H,1H,2H,2H-perfluoro-1-decanol, perfluoro(2,5-dimethyl-3,6-dioxane anionic) acid methyl ester, 2H-perfluoro-5-methyl-3,6-dioxanonane, 1H,1H,2H,3H,3H-perfluorononane-1,2-diol, 1H,1H,9H-perfluoro-1-nonanol, 1H,1H-perfluorooctanol, 1H,1H,2H,2H-perfluorooctanol, 2H-perfluoro-5,8,11,14-tetramethyl-3,6,9,12,15-pentaoxaoctadecane, perfluorotributylamine, perfluorotrihexylamine, methyl perfluoro-2,5,8-trimethyl-3,6,9-trioxadodecanoate, perfluorotripentylamine, perfluorotripropylamine, 1H,1H,2H,3H,3H-perfluoroundecane-1,2-diol, trifluorobutanol, 1,1,1-trifluoro-5-methyl-2,4-hexanedione, 1,1,1-trifluoro-2-propanol, 3,3,3-trifluoro-1-propanol, 1,1,1-trifluoro-2-propyl acetate, perfluorobutyltetrahydrofuran, perfluorodecalin, perfluoro(1,2-dimethylcyclohexane), perfluoro(1,3-dimethylcyclohexane), propylene glycol trifluoromethyl ether acetate, propylene glycol methyl ether trifluoromethyl acetate, butyl trifluoromethylacetate, methyl 3-trifluoromethoxypropionate, perfluorocyclohexanone, propylene glycol trifluoromethyl ether, butyl trifluoroacetate, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,3,3,3-hexafluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 2,2,3,4,4,4-hexafluoro-1-butanol, 2-trifluoromethyl-2-propanol, 2,2,3,3-tetrafluoro-1-propanol, 3,3,3-trifluoro-1-propanol, and 4,4,4-trifluoro-1-butanol, which may be used alone or in admixture.

Process

The invention also provides a pattern forming process comprising the steps of applying the aforementioned resist composition onto a substrate to form a coating, heat treating the coating, exposing it to high-energy radiation, and developing the exposed coating with a developer. The preferred high-energy radiation has a wavelength in the range of 180 to 250 nm.

The exposing step may be performed by immersion lithography involving exposing the coating to high-energy radiation through a liquid. In an exemplary embodiment of the immersion lithography, high-energy radiation having a wavelength of 180 to 250 nm is used, a liquid is introduced between the substrate having a resist coating and a protective coating formed thereon and a projection lens, and the substrate is exposed to the high-energy radiation through the liquid. An exemplary liquid is water.

In forming a resist pattern from the resist composition of the invention, any well-known lithography may be used. For example, the resist composition is applied onto a substrate (e.g., Si, SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG, low-dielectric-constant film, etc.) for integrated circuit microfabrication by a suitable coating technique such as spin coating. The coating is prebaked on a hot plate at 50 to 150° C. for about 1 to 10 minutes, preferably at 60 to 140° C. for 1 to 5 minutes. The resulting resist film is generally 10 to 200 nm thick.

By forming an antireflective coating (ARC) between the substrate for integrated circuit microfabrication and the photoresist, substrate reflection may be suppressed. Suitable antireflective coatings include inorganic coatings of amorphous carbon and SION and organic coatings formed by spin coating, with the latter being widely employed.

As the immersion lithography uses a projection lens having a NA in excess of 1 and allows the incident angle of light to the resist and ARC to increase, the prior-art single-layer ARC is difficult to control reflection. In this regard, bilayer ARC has been proposed. Also to overcome a lowering of etching margin by a thickness reduction of resist film, a trilayer process has been proposed involving forming a silicon-containing film as an underlay beneath the resist, and forming an undercoat layer with a high carbon density on a substrate for integrated circuit microfabrication. Films each consisting of one or more of many various layers may be formed beneath the photoresist.

After a photoresist layer is formed on a wafer, a water-insoluble, alkali-soluble resist protective coating material is applied to the photoresist layer by suitable techniques, typically spin coating. The coating thickness is preferably in a range of 10 to 500 nm. The lithography used herein may be either dry lithography wherein a gas such as air or nitrogen is present between the resist protective coating and the projection lens, or immersion lithography wherein a liquid fills in between the resist protective coating and the projection lens. The immersion lithography favors water. In the immersion lithography, whether or not the wafer edge and rear side are cleaned and the cleaning technique are important in preventing flowing of water to the wafer rear side and leaching from the substrate. After spin coating, the resist protective coating is baked at a temperature of 40 to 130° C. for 10 to 300 seconds for evaporating off the solvent. In the case of resist layer formation and dry lithography, edge cleaning is performed during the spin coating. In the case of immersion lithography, contact of water with the substrate surface which is fully hydrophilic is undesirable because water may be left on the substrate surface at the edge. It is then recommended to omit edge cleaning during the spin coating of the resist protective coating.

Once the resist protective coating is formed, exposure is carried out by immersion lithography. This is followed by post-exposure bake (PEB) and development in an alkaline developer for 10 to 300 seconds. An aqueous solution of 2.38 wt % tetramethylammonium hydroxide (TMAH), which is commonly used as the alkaline developer, is used herein. Sometimes water is left on the resist protective coating prior to PEB. If PEB is performed in the presence of residual water, water can penetrate through the protective coating to suck up the acid in the resist, impeding pattern formation. To fully remove the water on the protective coating prior to PEB, the water on the protective coating should be dried or recovered by suitable means, for example, spin drying prior to PEB, purging of the protective coating surface with dry air or nitrogen, or post-soaking after the exposure.

As discussed earlier, the photoresist layer formed from the resist composition of the invention substantially prevents formation of a mixed layer with the protective coating and remains fully hydrophilic after development, eliminating the occurrence of defects like residues known as blobs.

Resist materials for use with mask blanks often include novolac resins and hydroxystyrene based resins. Those resins in which hydroxyl groups are substituted by acid labile groups are used for positive resists while these resins in combination with crosslinking agents are used for negative resists. Base polymers which can be used herein include copolymers of hydroxystyrene with one or more of (meth)acrylic derivatives, styrenes, vinyl naphthalenes, vinyl anthracenes, vinyl pyrenes, hydroxyvinyl naphthalenes, hydroxyvinyl anthracenes, indenes, hydroxyindenes, acenaphthylenes, and norbornadienes.

Where the resist coating is for use with mask blanks, the photoresist composition of the invention is coated on a mask blank substrate of SiO₂, Cr, CrO, CrN, MoSi or the like. By further forming a SOG film and an organic undercoat film between the photoresist and the blank substrate, there is provided a three-layer structure which is also acceptable herein. Once the resist coating is formed, the structure is exposed using an electron beam writing system. The exposure is followed by post-exposure baking (PEB) and development in an alkaline developer for 10 to 300 seconds.

EXAMPLE

Examples of the invention are given below by way of illustration and not by way of limitation. The abbreviations used herein are GPC for gel permeation chromatography, NMR for nuclear magnetic resonance, Mw for weight average molecular weight, Mn for number average molecular weight, and Mw/Mn for molecular weight dispersity. Mw and Mn are determined by GPC versus polystyrene standards. All parts are by weight (pbw).

Preparation of Polymers

Additive polymers to be added to resist compositions were prepared by combining monomers, effecting copolymerization reaction in isopropyl alcohol as a solvent, pouring the polymerization solution into hexane for crystallization, washing the polymer with hexane, repeating the crystallization and washing steps, isolating and drying. The resulting polymers were analyzed for composition by ¹H-NMR and for Mw and Mw/Mn by GPC.

Preparation of Resist Compositions

Resist compositions, designated Resists 1 to 5, were prepared by combining and dissolving a base resin, a photoacid generator, and a basic compound in an organic solvent in accordance with the recipe shown below, and filtering through a Teflon® filter having a pore size of 0.2 μm. It is noted that Resists 1 to 4 are positive and Resist 5 having a crosslinker added thereto is negative.

Resist 1

Mixing Composition:

Base Resin 1 100 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw

Base Resin 1 has the following structural formula.

PAG-1: triphenylsulfonium nonafluoro- butanesulfonate Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine Organic solvent 1: 1-methoxyisopropyl acetate Organic solvent 2: cyclohexanone

Resist 2

Mixing Composition:

Base Resin 2 100 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw

Base Resin 2 has the following structural formula.

PAG-1: triphenylsulfonium nonafluoro- butanesulfonate Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine Organic solvent 1: 1-methoxyisopropyl acetate Organic solvent 2: cyclohexanone

Resist 3

Mixing Composition:

Base Resin 1 50 pbw Base Resin 3 50 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw 

Base Resin 3 has the following structural formula.

PAG-1: triphenylsulfonium nonafluoro- butanesulfonate Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine Organic solvent 1: 1-methoxyisopropyl acetate Organic solvent 2: cyclohexanone

Resist 4

Mixing Composition:

Base Resin 2 50 pbw Base Resin 4 50 pbw PAG-1  5 pbw Basic compound  1 pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw 

Base Resin 4 has the following structural formula.

PAG-1: triphenylsulfonium nonafluoro- butanesulfonate Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine Organic solvent 1: 1-methoxyisopropyl acetate Organic solvent 2: cyclohexanone

Resist 5

Mixing Composition:

Base Resin 5 100 pbw PAG-1  5 pbw Basic compound  1 pbw Crosslinker  10 pbw Organic solvent 1 1330 pbw  Organic solvent 2 570 pbw

Base Resin 5 has the following structural formula.

PAG-1: triphenylsulfonium nonafluoro- butanesulfonate Basic compound (Quencher 1): 2-cyclohexylcarboxyethylmorpholine Crosslinker: 1,3,4,6-tetramethoxymethyl- glycoluril Organic solvent 1: 1-methoxyisopropyl acetate Organic solvent 2: cyclohexanone Preparation of Protective Coating Material

Protective topcoat compositions, designated TC1 to TC3, were prepared by combining and dissolving a base resin (TC Polymer 1, 2 or 3) in an organic solvent in accordance with the recipe shown below, and filtering through a Teflon® filter having a pore size of 0.2 μm.

TC1 TC Polymer 1 100 pbw Organic solvent 3 2600 pbw  Organic solvent 4 260 pbw TC2 TC Polymer 2 100 pbw Organic solvent 3 2600 pbw  Organic solvent 4 260 pbw TC3 TC Polymer 3 100 pbw Organic solvent 3 2600 pbw  Organic solvent 4 260 pbw

TC Polymers 1 to 3 have the structural formula below.

TC Polymer 1 Mw 7,600 Mw/Mn 1.62

TC Polymer 2 Mw 8,300 Mw/Mn 1.68

TC Polymer 3 Mw 8,100 Mw/Mn 1.45

Organic solvent 3: isoamyl ether

Organic solvent 4: 2-methyl-1-butanol

Examples 1 to 24 and Comparative Examples 1 to 9

Resist coating solutions #1 to #18 were prepared by compounding the resist composition as a matrix with one of the above-prepared polymers (Polymers 1 to 14) in a suitable proportion. Tables 1 and 2 show a combination and proportion of the additive polymer and the matrix resist composition. It is noted that the proportion of the additive polymer is expressed in parts by weight per 100 parts by weight of the base resin in the matrix resist composition.

Each resist solution was applied onto an antireflective coating ARC-29A (Nissan Chemical Co., Ltd.) of 87 nm thick formed on a silicon substrate and baked at 110° C. for 60 seconds, forming a resist film of 150 nm thick. In Examples 18 to 23, a protective topcoat solution was coated thereon and baked at 100° C. for 60 seconds, forming a protective coating of 50 nm thick (TC1, TC2 or TC3). The structure was exposed by means of an ArF scanner model S307E (Nikon Corp., NA 0.85, σ 0.93, ⅘ annular illumination, 6% halftone phase shift mask), post-exposure baked (PEB) at 110° C. for 60 seconds, and developed with a 2.38 wt % TMAH aqueous solution for 60 seconds, forming a 75-nm line-and-space pattern over the wafer surface. Mask fidelity was examined by determining a mask error factor (MEF) of the 75-nm line-and-space pattern. MEF is given as measured linewidth variation/mask linewidth variation, with smaller values of MEF being better. A cross section of the wafer was then observed for comparing the pattern profile.

In Comparative Examples 1 to 9, the polymeric additive was not added. In Comparative Examples 6 to 9, the protective coating was applied.

TABLE 1 Pattern Matrix Protective Additive profile resist topcoat polymer after Resist solution composition material (amount) development MEF Example 1 Resist solution #1 Resist 1 — Polymer 1 Rectangular 3.2 (5 pbw) 2 Resist solution #2 Resist 1 — Polymer 2 Rectangular 3.4 (5 pbw) 3 Resist solution #3 Resist 1 — Polymer 3 Rectangular 3.4 (5 pbw) 4 Resist solution #4 Resist 1 — Polymer 4 Rectangular 3.3 (5 pbw) 5 Resist solution #5 Resist 1 — Polymer 5 Rectangular 3.8 (5 pbw) 6 Resist solution #6 Resist 1 — Polymer 6 Rectangular 3.6 (5 pbw) 7 Resist solution #7 Resist 1 — Polymer 7 Rectangular 3.6 (5 pbw) 8 Resist solution #8 Resist 1 — Polymer 8 Rectangular 3.8 (5 pbw) 9 Resist solution #9 Resist 1 — Polymer 9 Rectangular 3.4 (5 pbw) 10 Resist solution #10 Resist 1 — Polymer 10 Rectangular 3.2 (5 pbw) 11 Resist solution #11 Resist 1 — Polymer 11 Rectangular 3.3 (5 pbw) 12 Resist solution #12 Resist 1 — Polymer 12 Rectangular 4.0 (5 pbw) 13 Resist solution #13 Resist 1 — Polymer 13 Rectangular 3.5 (2 pbw) Polymer 1 (3 pbw) 14 Resist solution #14 Resist 1 — Polymer 14 Rectangular 3.9 (2 pbw) Polymer 1 (3 pbw) 15 Resist solution #15 Resist 2 — Polymer 7 Rectangular 3.2 (5 pbw) 16 Resist solution #16 Resist 3 — Polymer 7 Rectangular 3.7 (5 pbw) 17 Resist solution #17 Resist 4 — Polymer 7 Rectangular 3.6 (5 pbw) 18 Resist solution #18 Resist 5 — Polymer 7 Rectangular 5.2 (5 pbw) 19 Resist solution #1 Resist 1 TC1 Polymer 1 Rectangular 3.2 (5 pbw) 20 Resist solution #7 Resist 1 TC1 Polymer 7 Rectangular 3.4 (5 pbw) 21 Resist solution #12 Resist 1 TC1 Polymer 12 Rectangular 3.3 (5 pbw) 22 Resist solution #15 Resist 2 TC1 Polymer 7 Rectangular 3.1 (5 pbw) 23 Resist solution #1 Resist 1 TC2 Polymer 1 Rectangular 3.3 (5 pbw) 24 Resist solution #1 Resist 1 TC3 Polymer 1 Rectangular 3.2 (5 pbw)

TABLE 2 Pattern Matrix Protective Additive profile resist topcoat polymer after Resist solution composition material (amount) development MEF Comparative 1 — Resist 1 — — Somewhat 4.8 Example rounded top 2 — Resist 2 — — Rounded top 4.4 3 — Resist 3 — — Somewhat 4.8 rounded top 4 — Resist 4 — — Rounded top 4.8 5 — Resist 5 — — Bulged top 6.5 6 — Resist 1 TC1 — Rounded top 5.2 7 — Resist 3 TC1 — Heavily 5.3 rounded top 8 — Resist 1 TC2 — Heavily 5.2 rounded top 9 — Resist 1 TC3 — Rounded top 5.4

As is evident from Tables 1 and 2, the resist compositions having the inventive polymers compounded therein are improved in both rectangularity and MEF. Even when protective coatings are applied, these resist layers maintain a rectangularity and a MEF without degradation, and intermixing thereof with the protective coating is inhibited.

Examples 25 to 28 and Comparative Examples 10 to 11

Resist solutions #1, #7, #12 and #16 were selected from Tables 1 and 2. For each, a resist film was formed on a silicon substrate as in Examples 1 to 24. A contact angle with water of the photoresist film was measured, using an inclination contact angle meter Drop Master 500 by Kyowa Interface Science Co., Ltd. Specifically, 5 μL of deionized water was dispensed on the photoresist film after development. The results are shown in Table 3 (Examples 25 to 28). As comparative examples, the same test was carried out without adding the polymer of the invention. The results are also shown in Table 3 (Comparative Examples 10 and 11).

In a further run, resist solutions #1, #7, #12 and #16 were precision filtered through a high-density polyethylene filter with a pore size of 0.02 μm. Protective topcoat composition TC1 was similarly precision filtered. The resist solution was applied onto an antireflective coating ARC-29A (Nissan Chemical Co., Ltd.) of 87 nm thick formed on a 8-inch silicon substrate and baked at 110° C. for 60 seconds, forming a resist film of 150 nm thick. The protective topcoat solution TC1 was coated thereon and baked at 100° C. for 60 seconds. Using an ArF scanner model S307E (Nikon Corp., NA 0.85, σ 0.93, Cr mask), the entire surface of the wafer was subjected to checkered-flag exposure including alternate exposure of open-frame exposed and unexposed portions having an area of 20 mm square. This was followed by post-exposure baking (PEB) at 110° C. for 60 seconds and development with a 2.38 wt % TMAH aqueous solution for 30 seconds.

Using a flaw detector Win-Win 50-1200 (Tokyo Seimitsu Co., Ltd.), the number of defects in the unexposed portion of the checkered-flag was counted at the pixel size of 0.125 μm. The results are shown in Table 3. As comparative examples, the same test was carried out without adding the polymer of the invention. The results are also shown in Table 3 (Comparative Examples 10 and 11).

TABLE 3 Contact angle after Number development of Resist solution (°) defects Example 25 Resist solution #1 55 7 Example 26 Resist solution #7 50 3 Example 27 Resist solution #12 52 5 Example 28 Resist solution #16 55 6 Comparative Example 10 Resist 1 65 1,020 Comparative Example 11 Resist 3 68 2,300

As is evident from Table 3, the resist composition having the polymeric additive incorporated therein is successful in dramatically reducing the number of defects after development.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.

For example, although the resist composition applied to the immersion lithography has been described, it is also applicable to conventional lithography.

Japanese Patent Application No. 2007-086625 is incorporated herein by reference.

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A resist composition comprising a polymer which changes its alkali solubility under the action of an acid as a base resin, and a copolymer comprising recurring units containing a carboxylic acid ammonium salt and recurring units containing at least one fluorine atom as an additive.
 2. The resist composition of claim 1, wherein said copolymer has the general formula (1):

wherein R⁰, R³, R⁵, and R⁸ are each independently hydrogen or methyl, X₁ and Y₂ are each independently selected from the group consisting of a single bond, —O—R¹⁰—, —C(═O)—O—R¹⁰—, —C(═O)—NH—R¹⁰—, a straight or branched C₁-C₄ alkylene, and phenylene group, wherein R¹⁰ is a straight, branched or cyclic C₁-C₁₀ alkylene group which may contain an ester or ether group, n is 1 or 2, in case of n=1, Y₁ is selected from the group consisting of a single bond, —O—R¹⁰—, —C(═O)—O—R¹⁰—, —C(═O)—NH—R¹⁰—, a straight or branched C₁-C₄ alkylene, and phenylene group, wherein R¹⁰ is as defined above, in case of n=2, Y₁ is selected from the group consisting of —O—R¹⁰¹═, —C(═O)—O—R¹⁰¹═, —C(═O)—NH—R¹⁰¹═, a straight or branched C₁-C₄ alkylene group with one hydrogen atom eliminated, and a phenylene group with one hydrogen atom eliminated, wherein R¹⁰¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group with one hydrogen atom eliminated which may contain an ester or ether group, X₂ is selected from the group consisting of a single bond, —O—R¹¹—, —C(═O)—O—R¹¹—, a straight or branched C₁-C₄ alkylene, and phenylene group, wherein R¹¹ is a straight, branched or cyclic C₁-C₁₀ alkylene group which may contain an ester or ether group and may contain a fluorine atom, R¹ and R⁴ are each independently selected from the group consisting of hydrogen, a straight, branched or cyclic C₁-C₂₀ alkyl and a C₂-C₂₀ alkenyl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom, and a C₆-C₁₀ aryl group, plural R¹ or R⁴ may bond together to form a ring of 3 to 20 carbon atoms, R² is selected from the group consisting of a straight, branched or cyclic C₁-C₂₀ alkyl, C₂-C₂₀ alkenyl and C₆-C₁₄ aryl group which may contain a hydroxy, ether, ester, cyano, amino group, double bond or halogen atom, R⁶ is a straight, branched or cyclic C₁-C₁₂ alkylene group, R⁷ is hydrogen, fluorine, methyl, trifluoromethyl or difluoromethyl, or R⁷ may bond with R⁶ to form an aliphatic ring of 3 to 12 carbon atoms with the carbon atom to which they are attached, which ring may contain an ether group, fluorinated alkylene group or trifluoromethyl group, R⁹ is a straight, branched or cyclic C₁-C₂₀ alkyl group which has at least one fluorine atom substituted thereon and which may contain an ether, ester or sulfonamide group, the subscripts are numbers in the range: 0≦(a-1)<1.0, 0≦(a-2)<1.0, 0<(a-1)+(a-2)<1.0, 0≦(b-1)<1.0, 0≦(b-2)<1.0, 0<(b-1)+(b-2)<1.0, and 0.5≦(a-1)+(a-2)+(b-1)+(b-2)≦1.0.
 3. The resist composition of claim 1 which is a chemically amplified positive resist composition.
 4. The resist composition of claim 3, wherein the base resin is a polymer comprising recurring units having an acid labile group and recurring units having a hydroxy group and/or adhesive group of lactone ring.
 5. The resist composition of claim 1 which is a chemically amplified negative resist composition.
 6. The resist composition of claim 1, further comprising at least one member selected from the group consisting of an organic solvent, a basic compound, a dissolution regulator, a crosslinker, and a surfactant.
 7. A pattern forming process comprising the steps of: applying the resist composition of claim 1 onto a substrate to form a coating, heat treating the coating and exposing it to high-energy radiation, and developing the exposed coating with a developer.
 8. The process of claim 7, wherein the high-energy radiation has a wavelength of 180 to 250 nm.
 9. The process of claim 7, wherein the exposing step is by immersion lithography involving exposing the coating to high-energy radiation through a liquid.
 10. The process of claim 9, further comprising the step of forming a protective coating so that the protective coating intervenes between the photoresist coating and the liquid during the immersion lithography.
 11. The process of claim 10, wherein the protective coating is an alkali-soluble protective film based on a polymer having alpha-trifluoromethylhydroxy groups.
 12. The process of claim 9, wherein the immersion lithography involves using high-energy radiation having a wavelength of 180 to 250 nm, introducing a liquid between the substrate having a resist coating and a protective coating formed thereon and a projection lens, and exposing the substrate to the high-energy radiation through the liquid.
 13. The process of claim 9, wherein the liquid is water. 